It contains more molecules than atoms. It contains more electrons than protons. It is carrying an electric current. It is made of metal.
I gave my students this multiple choice question: Which of the following describes an object that must have a net negative charge?

Only one answer is correct among these 4 choices:
- It contains more molecules than atoms.
- It contains more electrons than protons.
- It is carrying an electric current.
- It is made of metal.

Could you tell me which one is correct?

It contains more electrons than protons.