__________ the task, they had to stay in the lab for another two hours.
| A．Not completing | B．Not completed |
| C．Not having completed | D．Having not completed |
______ to somebody, a British person often shakes hands with the stranger.
| A．Introducing | B．To introduce | C．To be introduced | D．On being introduced |
It was the hurricane ______ was called Katrina ______ destroyed the city of New Orleans.
| A．which; that | B．what; which | C．which; who | D．that; which |
____ the bike Smith had stolen ?
| A．Been | B．Did | C．Was | D．Had |
He looks very tired . He ____ to bed too late last night .
| A．must go | B．must have gone | C．could go | D．didn''t go |
The girl was frightened by the thief , and she stood there without ____ speak .
| A．daring to | B．daring | C．dare to | D．dared to |