IN: Which person is they?
The Drill Sergeants trained the troops aggressively so they could prepare them for the impending war.
OUT: The Drill Sergeants

IN: Which person is he?
The chef made breakfast for the captain because he required food.
OUT: the captain

IN: Which person is he?
Darth Vader said to Luke Skywalker, "I am your father", because he was his son.
OUT: Luke Skywalker

IN: Which person is they?
Retail stores have been trying to pass an internet tax on online retailers for the past few years, but they are adamant on fighting against this regulation they are trying to impose.
OUT:
online retailers