– Do you know why the river was polluted?
-- Many different factors ___________ the serious pollution of the river.
| A．contributed to | B．adjusted to | C．were accustomed to | D．were attached to |
21. Mary was so ___ in aprreciating the beautiful view that she didn't realize the weather was____.
| A．absorbing, frozen | B．absorbing, freezing | C．absorbed, frozen | D．absorbed, freezing |
20. The teenagers wonder what ______makes Jay a successful pop singer.
| A．is it | B．is it that | C．it is | D．it is that |
19. Johnson ______ for 5 years for political reasons when he was young.
| A．was put in prison | B．was in the prison | C．out in prison | D．was in prison |
二。单项选择题（共13分）
18. You are very ______ to be late again unless you get there by bus.
| A．likely | B．possible | C．probable | D．Proper |
35．You have broken your promise；you______painting the house long ago．
| A．could have finished | B．had better finish |
| C．must have finished | D．should have finished |