IN: Which person is they?
The police called headquarters for help and they continued to fight the criminals.
OUT: The police

IN: Which person is they?
Peacocks are considered very majestic birds by bird watchers, but they know it is just a perception of how they see things.
OUT: bird watchers

IN: Which person is it?
A monkey ate a lizard and it screamed in pain.
OUT: a lizard

IN: Which person is he?
John bought a beer for Bill because he likes cool guys.
OUT:
John