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: a plant 's roots slowly break down rocks as the roots grow
What is the most likely cause of split rocks on a mountain slope?

Fact: dropping an object into water causes vibrations in the water
Stepping in a lake causes?

Fact: precipitation is when water falls from the sky

Needing to use an umbrella could be the result of?