1. She has opened the window.
2. She has taken her copybook.
3. We have been here for more than half an hour.
4. Tom has seen this play, but i haven't.
5. Bob has gone out. He is not here.
6. We have tried to open the door, but we can't do it.
7. They have run out of milk and they must buy some.
8. Chris has bought a new car.
9. They have given me these pears.
10. I have forgotten to tell you about it.