Ladies and gentlemen, please fasten your seat belt. The plane __________.
| A．takes off | B．is taking off | C．has taken off | D．took off |
.While building a tunnel through the mountain, ________ .
| A．an underground lake was discovered | B．there was an underground lake discovered |
| C．a lake was discovered underground | D．the workers discovered an underground lake |
The train ________ arrive at 11∶30, but was an hour late.
| A．was about to | B．was likely to | C．was supposed to | D．was certain to |
.The two ladies are ________ the same age, but there seems to be ten years ________ them.
| A．at, between | B．about, among | C．as, among | D．of, between |
Paper produced every year is ________ the world's production of vehicles.
| A．the three times weight of | B．three times the weight of |
| C．as three times heavy as | D．three times as heavier as |
We have done things we ought not to have done and ______ undone things we ought to have done.
| A．left | B．leave | C．will leave | D．leaving |