Leonardo da Vince_____birds kept in cages in order to have the pleasure of setting them free.
| A．is said to be buying | B．is said to have bought |
| C．had said to buy | D．who said to have bought |
20. I got up early this morning, but I ________ so because I was not on duty today.
| A．mustn’t have done | B．needn’t have done |
| C．didn’t need to do | D．can’t have done |
19. It’s dangerous to have the fire _______ at home all night long.
| A．to burn | B．burn | C．burned | D．Burning |
18. I decided to write about Chaplin, one of ______ films I had seen several years before.
| A．whose | B．whom | C．that | D．which |
17. Our attention was drawn to the eight-year-old girl who was _______ perfectly at the piano.
| A．acting | B．behaving | C．performing | D．doing |
16. He made another wonderful discovery, __________ of great importance to science.
| A．I think which is | B．which I think it is | C．which I think it | D．which I think is |