QUES:
Who is they in the following sentence?

Buy More Book Store sends brand new books to customers because they like quality in the books they read.

ANS:
customers

QUES:
Who is he in the following sentence?

Student A beat student B, because he slacked off.

ANS:
student B

QUES:
Who is he in the following sentence?

Americans preferred Obama to McCain because he was younger.

ANS:
Obama