A solid changes to a gas. A liquid changes to a gas. A solid changes to a liquid. A liquid changes to a solid.
I gave my students this multiple choice question: Which of the following changes is caused by removing heat?

Only one answer is correct among these 4 choices:
- A solid changes to a gas.
- A liquid changes to a gas.
- A solid changes to a liquid.
- A liquid changes to a solid.

Could you tell me which one is correct?

A liquid changes to a solid.