Much labor would have been saved if the electronic computers_____________ before.
| A．had invented | B．were invented |
| C．should have been invented | D．had been invented |
Without facts, a person can not form a correct opinion, for he needs to have actual knowledge ______his thinking .
| A．on which to be based | B．on which to base |
| C．which to be based | D．which to base |
A few minutes earlier, and you would have seen the NBA star. But you ______.
| A．didn’t come | B．don’t come | C．haven’t come | D．won’t come |
He was told that it would be at least three more months _______he could recover and return to work.
| A．when | B．before | C．since | D．that |
---Where did the accident happen?
---It was at the post office near the Mansion Friendship ______ the peace talk would be held.
| A．where | B．which | C．that | D．When |
I dislike _________when others laugh at me in public or think poorly of me behind.
| A．that | B．those | C．it | D．them |