Thirty years ago this month，China's leaders launched an economic revolution.___________the door to free market reforms and foreign trade．
| A．to open | B．opened | C．opening | D．having opened |
—I didn’t know you were good friends .
—You_____.I have known her since she moved here. You were studying abroad then.
| A．may have | B．needn’t have | C．couldn’t have | D．must have |
— Mum, it’s none of my business. Why _____ I care?
— Just because she is your sister.
| A．can | B．should | C．will | D．may |
Why didn't you tell me there was no meeting today? I _____ all the way here _____the heavy snow.
| A．needn't have driven；through | B．can't have driven；across |
| C．mustn't have driven；through | D．shouldn't have driven；cross |
Michael______be a policeman, for he’s much too short.
| A．needn’t | B．can’t | C．should | D．may |
Peter______come with us tonight, but he isn’t very sure yet.
| A．must | B．may | C．can | D．will |