instruction:
Given a statement, generate a question such that the answer is contained in that statement.
question:
ice ages buried Earth in permafrost for millions of years at a time
answer:
How many years have ice ages buried Earth in permafrost?

question:
Tests are often done during science classes
answer:
What is often done during science classes?

question:
precipitation is essential for life on earth
answer:
What is essential for life on earth?