Do you know the boy ______ at the party last week?

5. Do you know the boy ______ at the party last week?
      A. we talked about            B. about him we talked
C. we talk about him            D. who we talked about him
6. The exercises which we are doing ______ very difficult.
A. is        B. has been        C. are            D. was
7. The machine ______ has now been repaired.
A. that broken down            C. that broke down
B. which are broken down        D. which broke