the size of the guitar. the metal on the guitar. the wood on the guitar. the vibrations of the string.
I gave my students this multiple choice question: When a guitar string is plucked, sound is produced by

Only one answer is correct among these 4 choices:
- the size of the guitar.
- the metal on the guitar.
- the wood on the guitar.
- the vibrations of the string.

Could you tell me which one is correct?

the vibrations of the string.