Which of these best defines the term "pollutant"?
===
OPTIONS:
- anything humans add to the atmosphere and oceans
- any substance that is harmful to the environment
- any substance that is a waste product of industry
- a substance that does not break down over time

any substance that is harmful to the environment

A layer of solid brittle rock comprises the outer 100 kilometers of Earth. This layer, which contains both the crust and the upper mantle, is called the
===
OPTIONS:
- core.
- sediment.
- lithosphere.
- hemisphere.

lithosphere.

Which two factors determine the gravitational attraction between two objects?
===
OPTIONS:
- time and temperature
- shape and orbital speed
- color and hardness
- mass and distance apart
mass and distance apart