The image shows the rover Curiosity's sky crane and the retrorockets that the sky crane used to place the rover on the surface of Mars. As the sky crane approached Mars, it fired its retrorockets so that the rover was slowly lowered onto the Martian surface. Which scientific concept best explains the action of the retrorockets?

The diagram represents a food web in a marine ecosystem. Which statement best describes the role of two populations within this food web?

The diagram represents a pendulum bob at four different positions along its path after the pendulum has been pulled to point A and released. Assuming that there is no energy lost due to friction, what is happening to the energy of the pendulum bob as it moves from point A to point B?

Two students are using a block and tackle as a machine to lift the engine out of a car. A block and tackle is a system of pulleys with a rope threaded between them. The students pull the rope 16 feet to lift the engine up 2 feet. What is the mechanical advantage of their machine?

A teacher is helping her class make an accurate scale model of the solar system on school grounds. The teacher says that the chalkboard will represent the Sun. She then hangs a painted softball 5.8 meters from the chalkboard to represent Mercury. At the back of the class, 15 meters from the chalkboard, the teacher hangs a blue-painted basketball to represent the Earth. About how far away from the chalkboard should the class mount the golf ball that will represent Neptune?

A scientist has a pure sample of an unknown metal that she is trying to identify. She measures the sample to have a mass of 25.1 g and a volume of 2.82 cm3. What should the scientist conclude that her sample is made of?

The table above summarizes some properties of the planets. The values for equatorial radius are an indicator of the planets' sizes—the longer the radius, the larger the planet. The maximum distance values are the distances of the planets when they are farthest away from the Sun in their orbits. Mean orbital speed is a measure of how fast the planets orbit the Sun. Based on the evidence shown above, which of the following statements is true?

The model here represents a chemical reaction. Which is a true statement about the reaction shown?

Humans depend on the ocean systems around the world for many purposes, including shipping goods, obtaining food, and participating in recreational activities. Many precautions are taken by both individuals and governments to protect ocean ecosystems, but negative impacts still occur as humans use and interact with the ocean and its organisms. Which of the following is an environmental impact caused by humans removing more resources from an ocean ecosystem than it can withstand?