Question

a scientist working in the middle of a desert found a rock with a fossil of a clam. the scientist knew that clams live in the sea. which could the fossil tell the scientist about the history of the desert​

Answer 1

It means that that fossil was probably in an ocean or water at the time. So the desert wasn't always a desert. So I agree with the other guy.

Answer 2

The fossil could tell the scientist that the dessert was once a sea