laughing at something funny. dogs doing tricks when told. doing your homework at the same time each day. salmon returning to their birthplace to lay their eggs.
I gave my students this multiple choice question: An example of an instinct is

Only one answer is correct among these 4 choices:
- laughing at something funny.
- dogs doing tricks when told.
- doing your homework at the same time each day.
- salmon returning to their birthplace to lay their eggs.

Could you tell me which one is correct?

salmon returning to their birthplace to lay their eggs.