Finish the sentences with the proper auxiliary verbs and perfect infinitive.
1. could have bought
2. shouldn't have invited
3. should have started
4. couldn't have been
5. needn't have phoned
6. couldn't have arrived
7. must have left
8. should have left
9. couldn't have finished
10. mustn't have left
11. shouldn't have eaten
12. could have passed
13. shouldn't have been
14. might have been
15. must have been
16. must have caused
17. needn't have walked - could have taken