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 different species existing at different times. Mass extinctions are periods where a large number of species go extinct. Fossils from different geological periods indicate that there have been multiple mass extinction events. For example, the extinction of the dinosaurs is a well - known mass extinction event. Earth is about 4.54 billion years old, so it is not a very young planet. Mammals did not exist in the early stages of Earth's history (e.g., during the time of the dinosaurs, mammals were very small and not the dominant group). The fossil record does not provide evidence that the amount of water on Earth has decreased over time.

Answer:

Mass extinctions have occurred several times on Earth.