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 am hesitating between 4 options to answer the following question, which option should I choose?
Question: Which of these is a safe practice in a laboratory investigation when working with chemicals?
Possibilities:
- 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

wearing safety goggles when working with chemicals