IN: Which person is they?
Coins are better than dollars because they weigh more.
OUT: Coins

IN: Which person is they?
Amazon offers a generous credit program for college books since they can be resold again to other buyers.
OUT: college books

IN: Which person is he?
George talked to Bill because he was nervous.
OUT: George

IN: Which person is they?
Students hate exams because they are lazy.
OUT:
Students