Given a fact, create a question that can be answered using the fact. Construct the question such that it is unambiguous, has a unique answer and the answer can be given using the fact.

Fact: if a tree is located near a sidewalk then the roots of that tree might crack the sidewalk
When tree roots grow, sometimes they?

Fact: as the activity of an animal increases , the amount of water in an animal 's body in that environment will decrease
What happens when animals in hot environments are active?

Fact: a radiator is a source of heat

A radiator is something that can?