Detailed Instructions: In this task, you are given a paragraph, and your task is to construct a question from the given passage. Construct question in such a way that (i) it is well explained in the paragraph, (ii) the words may/may not be present in the paragraph, (iii) it should start with what/how/describe. Avoid creating a question that (i) is just relevant to one or two sentences, and (ii) not relevant to passage. 
Problem:A plant or animal dies in mud or soil. The bones are all that remains. Over time the bones are covered in sediment. The sediment becomes rock. The rock becomes a fossil. 
Solution:
How are fossils formed?