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: classifying is when one sorts something by type
Sara sorted her marbles into glass ones and marbles made of crystal. This is an example of?

Fact: sunlight produces heat
Sunlight produces heat that causes?

Fact: if something is a raw material then that something comes directly from a source

Which is a source of raw materials?