IN: Which person is it?
The food in the refrigerator went bad because it was past the expiration date.
OUT: The food

IN: Which person is they?
The academic clubs lost their members because they were poorly funded.
OUT: The academic clubs

IN: Which person is they?
American Airlines offers upgrades for their preferred passengers so they continue choosing their airlines over others.
OUT: their preferred passengers

IN: Which person is he?
Brock understood the material better than Tracy because he was not paying attention.
OUT:
Tracy