III. Correct the error if necessary.
1. Since when are they waiting for us?
2. I have been looking for my passport since I came home.
3. His friend have been having this building for ten years.
4. Through the history people are always wanting to fight for new lands.
5. We received his letter a week ago and have tried to find time to write him back ever since.
6. Do you know where Nick is? I have looked for him for the past twenty minutes.

1. Since when have they been waiting for us?
  2. I have been looking for my passport since I returned home.
  3. His friend has had this building for ten years.
  4. Throughout history, people always want to fight for new lands.
  5. We received his letter a week ago and have since tried to find time to write him an answer.
  6. Do you know where Nick is? I have been looking for it for the last twenty minutes.