Carbon dioxide, which makes a _____ between us and the sun, prevents heat from getting out of the atmosphere easily, so the earth is becoming warmer.
| A．difference |
| B．comparison |
| C．connection |
| D．barrier |
_______ the tower building，where you can see the whole city．
| A．Standing on the top of | B．If you climb to |
| C．When you reach the top of | D．Get to the top of |
Why did they keep trying _________ they must have known it was hopeless?
| A．if | B．because | C．when | D．whether |
Having got up late this morning, Mike ran as fast as he could _______ to catch the bus.
| A．hope | B．to hope | C．hoped | D．hoping |
Their products enjoy 30 percent_____ of the market in this country because both the quality and their service are fine.
| A．share | B．profit | C．possession | D．advantage |
Although I admire you _____ your work on soil, I think you should apologize _____the villagers for the water pollution.
| A．for; to | B．to; for | C．for; for | D．to; to |