1. My friend had left when we arrived. Had my friend left when we arrived? No, my friend hadn't left when we arrived.

2. We had left an hour before he returned. Had we left an hour before he returned? No, we hadn't left an hour before he returned.

3. They had done that work by last Friday. Had they done that work by last Friday? No, they hadn't done that work by last Friday.

4. Before we went sightseeing we had studied the map. Had we studied the map before we went sightseeing? No, we hadn't studied the mao before we went sightseeing.

5 They had sold all the tickets by the time I called. Had they sold all the tickets by the time I called? No, they hadn't sold all the tickets by the time I called.

6. We had studied the train schedule before we went to the booking office. Had we studied the train schedule before we went to the booking office? No, we hadn't studied the train schedule before we went to the booking office.

7. By the time he came, we had cleaned the house. Had we cleaned the house by the time he came? No, we hadn't cleaned the house by the time he came.

8. They had paid all the bills before they left for home. Had they paid all the bills before they left for home? No, they hadn't paid all the bills before they left for home.

9. They had visited their granny before they left Moscow. Had they visited their granny before they left Moscow? No, they hadn't left their granny before they left Moscow.

10. Our manager had signed the contract when I came to the office. Had our manager signed the contract when I came to the office? No, our manager hadn't signed the contract when I came to the office.