Our plane delayed taking off as we ran into a storm. We were ________ for several hours at the airport, waiting for the storm to clear up.
| A．figured out | B．built up | C．held up | D．taken off |
—Why does the lake smell terrible?
—Because large quantities of water ________.
| A．have polluted | B．is being polluted |
| C．has been polluted | D．have been polluted |
His sister left home in 1998，and ________ since.
| A．had not been heard of | B．has not been heard of |
| C．had not heard of | D．has not heard of |
In the near future，more advances in the robot technology ________ by scientists.(2011·湖南)
| A．are making | B．are made |
| C．will make | D．will be made |
John, a friend of mine, who got married only last week, spent $3,000 more than he ________ for the wedding.
| A．will plan | B．has planned |
| C．would plan | D．had planned |
—Hurry up！Alice and Sue are waiting for you at the school gate.
—Oh！I thought they ________ without me.
| A．went | B．are going |
| C．have gone | D．had gone |