--Where's the library?

--________ is behind the gym.

1. A.
   They
2. B.
   It
3. C.
   Them
4. D.
   We

-- Where's the library?

-- ________ behind the offices.

1. A.
   It's
2. B.
   They're
3. C.
   He's
4. D.
   You're

The classroom is behind the library．(改为同义句)

　　The library is ______ ______ ______ the  classroom．