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

Input: Consider Input: Multiple genes mutations is usually necessary to develop cancer.

Output: What is usually necessary to develop cancer?


Input: Consider Input: You call the hard case that surrounds the soft parts of some animals the exoskeleton.

Output: What do you call the hard case that surrounds the soft parts of some animals?


Input: Consider Input: The fetal period lasts approximately 30 weeks weeks.


Output: Approximately how many weeks does the fetal period last?