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

Cancer occurs most often in adults over fifty age.
Cancer occurs most often in adults over what age?

Cranium (skull) is the term for the skeletal structure of the head that supports the face and protects the brain.
What is the term for the skeletal structure of the head that supports the face and protects the brain?

The lower density of warm air causes it to rise above cold air.

What property of warm air causes it to rise above cold air?

