Pour the acid into a trash can. Neutralize the acid before pouring it down a sink. Return the acid to the teacher's stock bottle. Allow the water to evaporate from the acid solution.
I am hesitating between 4 options to answer the following question, which option should I choose?
Question: In science class, a student obtains 20 mL of an acid solution. A small amount of acid is added to a substance to detect the presence of copper. What should be done with the excess acid solution?
Possibilities:
- Pour the acid into a trash can.
- Neutralize the acid before pouring it down a sink.
- Return the acid to the teacher's stock bottle.
- Allow the water to evaporate from the acid solution.

Neutralize the acid before pouring it down a sink.