What is Engineering?; | SD | Content Standards | Second Grade | 2-PS1-3 | Construct an evidence-based account of how an object made of a small set of pieces can be disassembled and made into a new object. | 1 |
Weathering & Erosion; Interactions of Earth’s Spheres; | SD | Content Standards | Fourth Grade | 4-ESS2-1 | Make observations and/or measurements to provide evidence of the effects of weathering or the rate of erosion by water, ice, wind, or vegetation. | 2 |
Weather vs. Climate; | SD | Content Standards | Third Grade | 3-ESS2-1 | Represent data in tables and graphical displays to describe typical weather conditions expected during a particular season. | 2 |
Weather vs. Climate; | SD | Content Standards | Third Grade | 3-ESS2-2 | Obtain and combine information to describe climates in different regions of the world. | 2 |
Wave Properties; | SD | Content Standards | Fourth Grade | 4-PS4-1 | Develop a model of waves to describe patterns in terms of amplitude and wavelength and to provide evidence that waves can cause objects to move. | 2 |
Water Quality & Distribution; Interactions of Earth’s Spheres; | SD | Content Standards | Fifth Grade | 5-ESS3-1 | Obtain and combine information about ways individual communities use science ideas to protect the Earth’s resources and environment. | 2 |
Water Quality & Distribution; | SD | Content Standards | Fifth Grade | 5-ESS2-2 | Describe and graph the amounts and percentages of water and fresh water in various reservoirs to provide evidence about the distribution of water on Earth. | 2 |
Water Cycle (3-5 Version); Interactions of Earth’s Spheres; | SD | Content Standards | Fifth Grade | 5-ESS2-1 | Develop a model to describe the interaction of geosphere, biosphere, hydrosphere, and/or atmosphere. | 2 |
Variation of Traits; | SD | Content Standards | Third Grade | 3-LS3-1 | Analyze and interpret data to provide evidence that plants and animals have traits inherited from parents and that variations of these traits exist in a group of similar organisms. | 2 |
Variation of Traits; | SD | Content Standards | Third Grade | 3-LS3-2 | Use evidence and reasoning to support the explanation that traits can be influenced by the environment. | 2 |
Variation of Traits; | SD | Content Standards | Third Grade | 3-LS4-2 | Use evidence and reasoning to construct an explanation for how the variations in characteristics among individuals of the same species may provide advantages in surviving, finding mates, and reproducing. | 2 |
Timescale of Earth's Events; | SD | Content Standards | Second Grade | 2-ESS1-1 | Use information from several sources to provide evidence that Earth events can occur quickly or slowly. | 1 |
Sunlight Warms the Earth; | SD | Content Standards | Kindergarten | K-PS3-1 | Make observations to determine the effect of sunlight on Earth’s surface. | 1 |
Sunlight Warms the Earth; | SD | Content Standards | Kindergarten | K-PS3-2 | Design and build a structure that will reduce the warming effect of sunlight on an area. | 1 |
Sun and Other Stars; | SD | Content Standards | Fifth Grade | 5-ESS1-1 | Support an argument that differences in the apparent brightness of the sun compared to other stars is due to distances from the Earth. | 2 |
Solids, Liquids and Gases; Material Properties and Purposes; | SD | Content Standards | Second Grade | 2-PS1-1 | Plan and carry out an investigation to describe and classify different kinds of materials by their observable properties. | 1 |
Renewable vs. Nonrenewable Resources; Energy Transfer; | SD | Content Standards | Fourth Grade | 4-PS3-4 | Design, test, and refine a device that converts energy from one form to another. | 2 |
Renewable vs. Nonrenewable Resources; | SD | Content Standards | Fourth Grade | 4-ESS3-1 | Obtain and combine information to describe that energy and fuels are derived from natural resources and their uses affect the environment. | 2 |
Reducing Our Impact on Earth; Natural Resources; | SD | Content Standards | Kindergarten | K-ESS3-3 | Communicate solutions that will reduce the impact of humans on the land, water, air, and/or other living things in the local environment. | 1 |
Pushes and Pulls; | SD | Content Standards | Kindergarten | K-PS2-1 | Plan and carry out an investigation to compare the effects of different strengths or different directions of pushes and pulls on the motion of an object. | 1 |
Pushes and Pulls; | SD | Content Standards | Kindergarten | K-PS2-2 | Analyze data to determine if a design solution works as intended to change the speed or direction of an object with a push or a pull. | 1 |
Properties of Matter; Chemical vs. Physical Changes; | SD | Content Standards | Fifth Grade | 5-PS1-4 | Conduct an investigation to determine whether the mixing of two or more substances results in new substances. | 2 |
Properties of Matter; | SD | Content Standards | Fifth Grade | 5-PS1-3 | Make observations and measurements to identify materials based on their properties. | 2 |
Pollination and Seed Dispersal; | SD | Content Standards | Second Grade | 2-LS2-2 | Develop a simple model that mimics the function of an animal in dispersing seeds or pollinating plants. | 1 |
Plant Growth Conditions; | SD | Content Standards | Second Grade | 2-LS2-1 | Plan and carry out an investigation to determine if plants need sunlight and water to grow. | 1 |
Patterns of Motion & Friction; | SD | Content Standards | Third Grade | 3-PS2-2 | Make observations and/or measurements of an object’s motion to provide evidence for how a pattern can be used to predict future motion. | 2 |
Patterns in the Sky; | SD | Content Standards | First Grade | 1-ESS1-1 | Use observations of the sun, moon, and stars to describe patterns that can be predicted. | 1 |
Particle Nature of Matter; | SD | Content Standards | Fifth Grade | 5-PS1-1 | Develop a model to describe that matter is made of particles too small to be seen. | 2 |
Oceans, Lakes and Rivers; | SD | Content Standards | Second Grade | 2-ESS2-3 | Obtain information to identify where water is found on Earth and that it can be solid or liquid. | 1 |
Natural Disasters; | SD | Content Standards | Fourth Grade | 4-ESS2-2 | Analyze and interpret data from maps to describe patterns of Earth’s features. | 2 |
Material Properties and Purposes; | SD | Content Standards | Second Grade | 2-PS1-2 | Analyze data obtained from testing different materials to determine which materials have the properties that are best suited for an intended purpose. | 1 |
Maps of Landforms; | SD | Content Standards | Second Grade | 2-ESS2-2 | Develop a model to represent the shapes and kinds of land and bodies of water in an area. | 1 |
Magnets & Static Electricity; | SD | Content Standards | Third Grade | 3-PS2-3 | Ask questions about cause and effect relationships of electric or magnetic interactions between two objects not in contact with each other. | 2 |
Magnets & Static Electricity; | SD | Content Standards | Third Grade | 3-PS2-4 | Define a simple design problem that can be solved by applying scientific ideas about magnets. | 2 |
Living vs. Non-Living Things; Plants Need Water And Light; Animals Need Food; | SD | Content Standards | Kindergarten | K-LS1-1 | Describe patterns of what plants and animals (including humans) need to survive. | 1 |
Living Things Change Their Environment; | SD | Content Standards | Kindergarten | K-ESS2-2 | Engage in argument from evidence for how plants and animals (including humans) can change the environment to meet their needs. | 1 |
Light Reflection & Vision; | SD | Content Standards | Fourth Grade | 4-PS4-2 | Develop a model to describe how light reflecting from objects and entering the eye allows objects to be seen. | 2 |
Introduction to Weather; | SD | Content Standards | Kindergarten | K-ESS2-1 | Use and share observations of local weather conditions to describe patterns over time. | 1 |
Introduction to Weather; | SD | Content Standards | Kindergarten | K-ESS3-2 | Ask questions to obtain information about the purpose of weather forecasting to prepare for, and respond to, severe weather. | 1 |
Introduction to Traits; | SD | Content Standards | First Grade | 1-LS3-1 | Construct an evidence-based account that young plants and animals are like, but not exactly like, their parents. | 1 |
Introduction to Sound; | SD | Content Standards | First Grade | 1-PS4-1 | Plan and carry out an investigation to provide evidence that vibrating materials can make sound and that sound can make materials vibrate. | 1 |
Introduction to Light; | SD | Content Standards | First Grade | 1-PS4-2 | Construct an evidence-based account for how objects can be seen only when illuminated. | 1 |
Introduction to Light; | SD | Content Standards | First Grade | 1-PS4-3 | Plan and carry out an investigation to determine the effect of placing objects made with different materials in the path of a beam of light. | 1 |
Inspired by Nature (Biomimicry); | SD | Content Standards | First Grade | 1-LS1-1 | Design a solution to a human problem by mimicking how plants and/or animals use their external parts to help them survive, grow, and meet their needs. | 1 |
Information Transfer; | SD | Content Standards | Fourth Grade | 4-PS4-3 | Create and compare multiple solutions that use patterns to transfer information. | 2 |
How Do We Use Food; Food Webs; | SD | Content Standards | Fifth Grade | 5-PS3-1 | Use models to describe that energy in animals’ food (used for body repair, growth, motion, and to maintain body warmth) was once energy from the sun. | 2 |
How Do We Use Food; Food Webs; | SD | Content Standards | Fifth Grade | 5-LS2-1 | Develop a model to describe the movement of matter and energy among producers, consumers, decomposers, and the environment. | 2 |
How Do We Use Food; | SD | Content Standards | Fifth Grade | 5-LS1-1 | Support an argument that plants get the materials they need for growth chiefly from air and water. | 2 |
Heating and Cooling; | SD | Content Standards | Second Grade | 2-PS1-4 | Construct an argument using reasoning and evidence that some changes caused by heating or cooling can be reversed and some cannot. | 1 |
Habitats; | SD | Content Standards | Kindergarten | K-ESS3-1 | Use a model to represent the relationship between the needs of different plants or animals (including humans) and the places they live. | 1 |
Four Seasons and Day Length; | SD | Content Standards | First Grade | 1-ESS1-2 | Make observations at different times of the year to relate the amount of daylight to the time of year. | 1 |
Fossils & Extinction; Earth's Landscapes; | SD | Content Standards | Third Grade | 3-LS4-1 | Analyze and interpret data from fossils to provide evidence of the organisms and the environments in which they lived long ago. | 2 |
Extreme Weather Solutions; Natural Disasters; | SD | Content Standards | Fourth Grade | 4-ESS3-2 | Generate and compare multiple solutions to reduce the impacts of natural Earth processes on humans. | 2 |
Extreme Weather Solutions; | SD | Content Standards | Third Grade | 3-ESS3-1 | Make a claim about the merit of a design solution that reduces the impacts of a weather-related hazard. | 2 |
Energy Transfer; Wave Properties; | SD | Content Standards | Fourth Grade | 4-PS3-2 | Make observations to provide evidence for how energy can be transferred from place to place by sound, light, heat, and electric currents. | 2 |
Ecosystems; Adaptations and the Environment; | SD | Content Standards | Third Grade | 3-LS4-3 | Construct an argument with evidence how some organisms thrive, some struggle to survive, and some cannot survive in a particular habitat. | 2 |
Ecosystems; | SD | Content Standards | Third Grade | 3-LS4-4 | Make a claim about the merit of a solution to a problem caused when the environment changes and the types of plants and animals that live there may change. | 2 |
Earth’s Orbit and Rotation; | SD | Content Standards | Fifth Grade | 5-ESS1-2 | Represent data in graphical displays to reveal patterns of daily changes in length and direction of shadows, day and night, and the seasonal appearance of some stars in the night sky. | 2 |
Earth's Landscapes; | SD | Content Standards | Fourth Grade | 4-ESS1-1 | Identify evidence from patterns in rock formations and fossils in rock layers to support an explanation for changes in a landscape over time. | 2 |
Conservation of Matter; | SD | Content Standards | Fifth Grade | 5-PS1-2 | Measure and graph quantities to provide evidence that regardless of the type of change that occurs when heating, cooling, or mixing substances, the total weight of matter is conserved. | 2 |
Communication Over Distances; | SD | Content Standards | First Grade | 1-PS4-4 | Design and build a device that uses light or sound to solve the problem of communicating over a distance. | 1 |
Collisions; | SD | Content Standards | Fourth Grade | 4-PS3-1 | Use evidence to construct an explanation relating the speed of an object to the energy of that object. | 2 |
Collisions; | SD | Content Standards | Fourth Grade | 4-PS3-3 | Ask questions and predict outcomes about the changes in energy that occur when objects collide. | 2 |
Changing the Shape of Land; | SD | Content Standards | Second Grade | 2-ESS2-1 | Compare multiple solutions designed to slow or prevent wind or water from changing the shape of the land. | 1 |
Brain Processing of Senses; Human Body Systems; Structure of Living Things; Adaptations and the Environment; | SD | Content Standards | Fourth Grade | 4-LS1-1 | Construct an argument that plants and animals have internal and external structures that function to support survival, growth, behavior, and reproduction. | 2 |
Brain Processing of Senses; | SD | Content Standards | Fourth Grade | 4-LS1-2 | Use a model to describe that animals receive different types of information through their senses, process the information in their brain, and respond to the information in different ways. | 2 |
Biodiversity of Life on Earth; | SD | Content Standards | Second Grade | 2-LS4-1 | Make observations of plants and animals to compare the diversity of life in different habitats. | 1 |
Balanced & Unbalanced Forces; | SD | Content Standards | Third Grade | 3-PS2-1 | Plan and carry out an investigation to provide evidence of the effects of balanced and unbalanced forces on the motion of an object. | 2 |
Balanced & Unbalanced Forces; | SD | Content Standards | Fifth Grade | 5-PS2-1 | Support an argument that the gravitational force exerted by Earth on objects is directed down. | 2 |
Animals Help Their Babies Survive; | SD | Content Standards | First Grade | 1-LS1-2 | Read texts and use media to determine patterns in behavior of parents and offspring that help offspring survive. | 1 |
Animal Group Behavior; | SD | Content Standards | Third Grade | 3-LS2-1 | Construct an argument that some animals form groups that help members survive. | 2 |
Animal & Plant Life Cycles; | SD | Content Standards | Third Grade | 3-LS1-1 | Develop models to describe that organisms have unique and diverse life cycles but all have in common birth, growth, reproduction, and death. | 2 |
Atoms & Molecules; | SD | Content Standards | MS Physical Science | MS-PS1-1 | Develop models to describe the atomic composition of simple molecules and extended structures. | |
Chemical Reactions; | SD | Content Standards | MS Physical Science | MS-PS1-2 | Analyze and interpret data on the properties of substances before and after the substances interact to determine if a chemical reaction has occurred. | |
Synthetic Materials; | SD | Content Standards | MS Physical Science | MS-PS1-3 | Obtain and evaluate information to describe that synthetic materials come from natural resources and impact society. | |
Intro to Thermal Energy; | SD | Content Standards | MS Physical Science | MS-PS1-4 | Develop a model that predicts and describes changes in particle motion, temperature, and state of a pure substance when thermal energy is added or removed. | |
Chemical Reactions; | SD | Content Standards | MS Physical Science | MS-PS1-5 | Develop and use a model to describe how the total number of atoms does not change in a chemical reaction and thus mass is conserved. | |
Intro to Thermal Energy; | SD | Content Standards | MS Physical Science | MS-PS1-6 | Design, construct, test, and modify a device that either releases or absorbs thermal energy by chemical processes. | |
Newton’s Laws of Motion; | SD | Content Standards | MS Physical Science | MS-PS2-1 | Design a solution to a problem involving the motion of two colliding objects that illustrates Newton’s Third Law. | |
Newton’s Laws of Motion; | SD | Content Standards | MS Physical Science | MS-PS2-2 | Plan an investigation to provide evidence that the change in an object’s motion depends on the sum of the forces on the object and the mass of the object. | |
Electric & Magnetic Fields; | SD | Content Standards | MS Physical Science | MS-PS2-3 | Ask questions about data to determine the factors that affect the strength of electric and magnetic forces. | |
Gravitational Forces Between Objects; | SD | Content Standards | MS Physical Science | MS-PS2-4 | Construct and present arguments using evidence to support the claim that gravitational interactions are attractive and depend on the masses of interacting objects. | |
Electric & Magnetic Fields; | SD | Content Standards | MS Physical Science | MS-PS2-5 | Conduct an investigation and evaluate the experimental design to provide evidence that fields exist between objects exerting forces on each other even though the objects are not in contact. | |
Potential vs. Kinetic Energy; | SD | Content Standards | MS Physical Science | MS-PS3-1 | Construct and analyze graphical displays of data to describe the relationships of kinetic energy to the mass of an object and to the speed of an object. | |
Potential vs. Kinetic Energy; | SD | Content Standards | MS Physical Science | MS-PS3-2 | Develop a model to describe that when the arrangement of objects interacting at a distance changes, different amounts of potential energy are stored in the system. | |
Heat: Transfer of Thermal Energy; | SD | Content Standards | MS Physical Science | MS-PS3-3 | Design, construct, and test a device that either minimizes or maximizes thermal energy transfer. | |
Heat: Transfer of Thermal Energy; | SD | Content Standards | MS Physical Science | MS-PS3-4 | Plan an investigation to determine the relationships among the energy transferred, the type of matter, the mass, and the change in the average kinetic energy of the particles as measured by the temperature of the sample. | |
Potential vs. Kinetic Energy; | SD | Content Standards | MS Physical Science | MS-PS3-5 | Engage in argument from evidence to support the claim that when the kinetic energy of an object changes, energy is transferred to or from the object. | |
Wave Reflection, Absorption & Transmittance; | SD | Content Standards | MS Physical Science | MS-PS4-1 | Use mathematical representations to describe a simple model for waves that includes how the amplitude of a wave is related to the energy in a wave. | |
Wave Reflection, Absorption & Transmittance; | SD | Content Standards | MS Physical Science | MS-PS4-2 | Develop and use a model to describe how waves are reflected, absorbed, or transmitted through various materials. | |
Digital vs. Analog Signals; | SD | Content Standards | MS Physical Science | MS-PS4-3 | Obtain, evaluate and communicate information to support the claim that digitized signals are a more reliable way to encode and transmit information than analog signals. | |
Plant & Animal Cells; | SD | Content Standards | MS Life Science | MS-LS1-1 | Plan and carry out an investigation to provide evidence that living things are made of cells; either one cell or many different types and numbers of cells. | |
Plant & Animal Cells; | SD | Content Standards | MS Life Science | MS-LS1-2 | Develop and use a model to describe the function of a cell as a whole and ways parts of cells contribute to the function. | |
Multicellular Organisms; | SD | Content Standards | MS Life Science | MS-LS1-3 | Construct an argument supported by evidence for how the body is a system of interacting subsystems composed of groups of cells. | |
Reproduction of Living Things; | SD | Content Standards | MS Life Science | MS-LS1-4 | Construct an argument based on empirical evidence and scientific reasoning to support an explanation for how characteristic animal behaviors and specialized plant structures affect the probability of successful reproduction of animals and plants respectively. | |
Competition in Ecosystems; | SD | Content Standards | MS Life Science | MS-LS1-5 | Construct a scientific explanation based on evidence for how environmental and genetic factors influence the growth of organisms. | |
Photosynthesis & Respiration; | SD | Content Standards | MS Life Science | MS-LS1-6 | Construct a scientific explanation based on evidence for the role of photosynthesis in the cycling of matter and flow of energy into and out of organisms. | |
Food Webs: Cycling of Matter & Flow of Energy; | SD | Content Standards | MS Life Science | MS-LS1-7 | Develop a model to describe how food is rearranged through chemical reactions forming new molecules that support growth and/or release energy as this matter moves through an organism. | |
Competition in Ecosystems; | SD | Content Standards | MS Life Science | MS-LS2-1 | Analyze and interpret data to provide evidence for the effects of resource availability on organisms and populations of organisms in an ecosystem. | |
Symbiosis (Interactions Between Organisms); | SD | Content Standards | MS Life Science | MS-LS2-2 | Construct an explanation that predicts patterns of interactions among organisms across multiple ecosystems. | |
Food Webs: Cycling of Matter & Flow of Energy; | SD | Content Standards | MS Life Science | MS-LS2-3 | Develop a model to describe the cycling of matter and flow of energy among living and nonliving parts of an ecosystem. | |
Competition in Ecosystems; | SD | Content Standards | MS Life Science | MS-LS2-4 | Construct an argument supported by empirical evidence that changes to physical or biological components of an ecosystem affect populations. | |
Maintaining Biodiversity; | SD | Content Standards | MS Life Science | MS-LS2-5 | Evaluate competing design solutions for maintaining biodiversity and ecosystem services. | |
Genes & Mutations; | SD | Content Standards | MS Life Science | MS-LS3-1 | Develop and use a model to describe why structural changes to genes (mutations) located on chromosomes may affect proteins and may result in harmful, beneficial, or neutral effects to the structure and function of the organism. | |
Reproduction of Living Things; | SD | Content Standards | MS Life Science | MS-LS3-2 | Develop and use a model to describe why asexual reproduction results in offspring with identical genetic information and sexual reproduction results in offspring with genetic variation. | |
The Fossil Record; | SD | Content Standards | MS Life Science | MS-LS4-1 | Analyze and interpret data for patterns in the fossil record that document the existence, diversity, extinction, and change of life forms throughout the history of life on Earth. | |
Comparative Anatomy; | SD | Content Standards | MS Life Science | MS-LS4-2 | Apply scientific ideas to construct an explanation for similarities and differences among modern organisms and between modern and fossil organisms to infer evolutionary relationships. | |
Natural Selection; | SD | Content Standards | MS Life Science | MS-LS4-4 | Construct an explanation based on evidence that describes how genetic variations of traits in a population increase some individuals’ probability of surviving and reproducing in a specific environment. | |
Biotechnology; | SD | Content Standards | MS Life Science | MS-LS4-5 | Obtain, evaluate, and communicate information about how technological advances have changed the way humans influence the inheritance of desired traits in organisms. | |
Natural Selection; | SD | Content Standards | MS Life Science | MS-LS4-6 | Use mathematical representations to support explanations of how natural selection may lead to increases and decreases of specific traits in populations over time. | |
Solar & Lunar Eclipses; | SD | Content Standards | MS Earth/Space Science | MS-ESS1-1 | Develop and use a model of the Earth-sun-moon system to describe the cyclic patterns of lunar phases, eclipses of the sun and moon, and seasons. | |
The Solar System; | SD | Content Standards | MS Earth/Space Science | MS-ESS1-2 | Develop and use a model to describe the role of gravity in the motions within galaxies and the solar system. | |
The Solar System; | SD | Content Standards | MS Earth/Space Science | MS-ESS1-3 | Analyze and interpret data to determine scale properties of objects in the solar system. | |
Rocks & Minerals (Including Rock Cycle); | SD | Content Standards | MS Earth/Space Science | MS-ESS2-1 | Develop a model to describe the cycling of Earth’s materials and the flow of energy that drives this process. | |
Tectonic Plates; | SD | Content Standards | MS Earth/Space Science | MS-ESS2-2 | Construct an explanation based on evidence for how geoscience processes have changed Earth’s surface at varying time and spatial scales. | |
Tectonic Plates; | SD | Content Standards | MS Earth/Space Science | MS-ESS2-3 | Analyze and interpret data on the age of the Earth, distribution of fossils and rocks, continental shapes, and seafloor structures to provide evidence of the past plate motions. | |
Water Cycle (6-8 Version); | SD | Content Standards | MS Earth/Space Science | MS-ESS2-4 | Develop a model to describe the cycling of water through Earth’s systems driven by energy from the sun and the force of gravity. | |
Air Masses & Weather Fronts; | SD | Content Standards | MS Earth/Space Science | MS-ESS2-5 | Collect data to provide evidence for how the motions and complex interactions of air masses results in changes in weather conditions. | |
Climate Zones & Ocean Currents; | SD | Content Standards | MS Earth/Space Science | MS-ESS2-6 | Develop and use a model to describe how unequal heating and rotation of the Earth cause patterns of atmospheric and oceanic circulation that determine regional climates. | |
Natural Resource Distribution; | SD | Content Standards | MS Earth/Space Science | MS-ESS3-1 | Construct a scientific explanation based on evidence for how the uneven distributions of Earth’s mineral, energy, and groundwater resources are the result of past and current geoscience processes. | |
Predicting Natural Disasters; | SD | Content Standards | MS Earth/Space Science | MS-ESS3-2 | Analyze and interpret data on natural hazards to forecast future catastrophic events and inform the development of technologies to mitigate their effects. | |
Human Impacts on the Environment; | SD | Content Standards | MS Earth/Space Science | MS-ESS3-3 | Apply scientific principles to design a method for monitoring and minimizing a human impact on the environment. | |
Human Impacts on the Environment; | SD | Content Standards | MS Earth/Space Science | MS-ESS3-4 | Construct an argument supported by evidence for how increases in human population and per-capita consumption of natural resources impact Earth’s systems. | |
Intro to Climate Change; | SD | Content Standards | MS Earth/Space Science | MS-ESS3-5 | Ask questions to clarify evidence of the factors that may have caused a change in global temperatures over the past century. | |