_____ he met with the difficulty did he realize the importance of group work.
| A．Even though | B．Not until | C．Only before | D．Ever since |
Nowadays, a large number of women, especially those from the countryside, _________ in the clothing industry.
| A．is working | B．works | C．work | D．worked |
The policeman's attention was suddenly caught by a small box which ______ placed under the Minister's car.
| A．has been | B．was being | C．had been | D．would be |
Years ago we didn't know this, but recent science ______ that people who don't sleep well soon get ill.
| A．showed | B．has shown | C．will show | D．is showing |
Since I won the big prize, my telephone hasn't stopped ringing. People ____to ask how I am going to spend the money.
| A．phone | B．will phone | C．were phoning | D．are phoning |
John ___ be a basketball player.He’s much too short.
| A．may | B．mustn’t | C．can't | D．should |