Given scientific fact as input, generate the question from this fact such that it can be answered from the input.

Multiple genes mutations is usually necessary to develop cancer.
What is usually necessary to develop cancer?

A student should use a balance to compare the masses of two small rocks.
Which tool should a student use to compare the masses of two small rocks?

Microevolution is the process by which organisms change in small ways over time.

What is the process by which organisms change in small ways over time?