You are presented with the quiz "Fossils are formed when remains of living things are what?" 

But you don't know the answer, so you turn to your teacher to ask for hints. He says that "fossils are formed when layers of sediment cover the remains of organisms over time" and "fossil fuels are formed from the remains of once living organisms that depended on light". 

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


 

   covered over time        