Many wines improve____ age, and it is the same with friendship.
| A．with | B．to | C．alongside | D．for |
31._____for a strong and fair climate agreement at the key UN summit in Copenhagen, 50,000 people in London wore blue and went to the streets.
| A．Call | B．Calling | C．To call | D．Called |
30. It is the test system, rather than the teachers,______is to blame for the students’ heavy burden nowadays.
| A．who | B．this | C．that | D．Whom |
29. The moment we heard of the accident, we____the work to rescue those trapped in the mine.
| A．set off | B．set down | C．set back | D．set about |
28. You can’t complain of being lonely____you don’t make any effort to communicate with others.
| A．when | B．until | C．unless | D．Once |
27. The boy was busy doing his homework, only_____once in a while to look out of the window.
| A．stopping | B．to stop | C．stopped | D．having stopped |