instruction:
Given a statement, generate a question such that the answer is contained in that statement.
question:
The softest mineral is used for making writing lead
answer:
What is the softest mineral used to make?


question:
Cryptic coloration is used for protection by fish against predators
answer:
What is used for protection by fish against predators?


question:
at least two mirrors are used for observing stars by astronomers
answer:

How many mirrors are used for observing stars by astronomers?