I know Mr Brown；we ＿＿＿＿＿＿ to each other at an international conference.
| A．are introduced | B．have been introduced |
| C．were introduced | D．had been introduced |
After living there for one year, they have ____ there.
| A．accustomed to working | B．accustomed to work |
| C．been accustomed to work | D．been accustomed to working |
He didn’t make _____ clear why he was late again.
| A．it | B．that | C．this | D．those |
I can hardly imagine Peter ____ across the Atlantic Ocean in five days.
| A．sail | B．to sail | C．sailing | D．to have sailed |
I wish I ____ clever enough to work out the ____ geometry problem.
| A．can be; abstract | B．could be; abstract |
| C．can be; easy | D．could be; easy |
If I ____ more about diamond, I ____ cheated by that man.
| A．had known, would not be | B．had known; wouldn’t have been |
| C．knew; would not have been | D．had known; would never be |