IN: Which person is it?
The bee landed on the flower because it had pollen.
OUT: the flower

IN: Which person is he?
The other student corrected Robert because he better understood the problem.
OUT: The other student

IN: Which person is they?
The sailors fell off the boats because they were capsizing.
OUT: the boats

IN: Which person is it?
The mouse ran from the cat all the way to the kitchen because it chased him.
OUT:
the cat