pouring unused chemicals down the sink mixing leftover chemicals in one container wearing safety goggles when working with chemicals returning unused chemicals to the original container
I gave my students this multiple choice question: Which of these is a safe practice in a laboratory investigation when working with chemicals?

Only one answer is correct among these 4 choices:
- pouring unused chemicals down the sink
- mixing leftover chemicals in one container
- wearing safety goggles when working with chemicals
- returning unused chemicals to the original container

Could you tell me which one is correct?

wearing safety goggles when working with chemicals