– I ran 10 miles last weekend. Can you believe that?
– Wow, that ______ easy!
| A．mustn' t be | B．mustn't have been |
| C．can't have been | D．couldn’t be |
The old man has retired from the factory. He _____ there for 30 years.
| A．works | B．worked |
| C．has worked | D．was working |
— I don’t mind telling you what I know.
— You _______. I can manage it myself.
| A．mustn’t | B．ought not to |
| C．can’t | D．don’t have to |
The boys enjoy playing basketball __________ many of the girls relax by playing ping-pong.
| A．while | B．or | C．since | D．if |
The teacher asked the students to do the experiment __________ small groups.
| A．to | B．for | C．on | D．in |
The website is very popular. And it’s amazing that __________ designer of it is just __________ nine-year-old child.
| A．the; the | B．a; the | C．the; a | D．a; a |