You are presented with the quiz "Fossils are found in places that were previously covered in what?" 

But you don't know the answer, so you turn to your teacher to ask for hints. He says that "if fossils of a water animal or plant are found in a place then that place used to be covered by water in the past" and "common fossils include plant fossils like ferns". 

So, what's the best answer to the question?


 

     water      