IN: Which person is they?
The construction company could not rezone the area due to endangered butterflies since they could not violate state law and endanger a species.
OUT: The construction company

IN: Which person is he?
Jackie Chan learned some things from watching Bruce Lee because he was a popular kung fu actor in the past.
OUT: Jackie Chan

IN: Which person is they?
Professors do a lot for students, but they are rarely thankful.
OUT: students

IN: Which person is she?
Kate Middleton is viewed as a newer generation Princess Diana because she is also being compared as a fashion symbol.
OUT:
Kate Middleton