Question

which statement explains something that the fossil record indicates?
earth is is still a very young planet
mammals have always existed on earth.
mass extinctions have occurred several times on earth.
the amount of water on earth has decreased over time.

Explanation:

The fossil record shows evidence of multiple mass - extinction events where large numbers of species went extinct. Earth is billions of years old, mammals did not always exist, and the fossil record is not the main source for information on Earth's water amount changes.

Answer:

Mass extinctions have occurred several times on Earth.