It feels like a rock. It smells like a lemon. It is colorless. It is hard.
I gave my students this multiple choice question: Which of the following is a property of CO2 gas?

Only one answer is correct among these 4 choices:
- It feels like a rock.
- It smells like a lemon.
- It is colorless.
- It is hard.

Could you tell me which one is correct?

It is colorless.