Some people fear that ________ air pollution may bring about changes in _______ weather around the world.
| A．/; the | B．the; / | C．an; the | D．the; a |
22．I’m terribly sorry to turn you down this time, but I promise I will ________ to you next time.
| A．pick it up | B．make it up | C．turn it up | D．set it up |
21．The moment we heard the news of the earthquake, we began to ________ the work to rescue those who were trapped in the building.
| A．set off | B．set down | C．set aside | D．set about |
20. When Jane began to take swimming lessons, her main__________was the fear of water.
| A．evidence | B．crisis | C．obstacle | D．Danger |
19. The language used in advertisements differs from____________used in ordinary readings.
| A．which | B．what | C．that | D．It |
18._________is often the case, he didn’t study hard and failed to pass the test.
| A．What | B．Which | C．It | D．As |