___________ the chapter four times, and I finally understand the author’s theory．
| A．Reading | B．Having read | C．To read | D．Read |
Once new difficulties ________in your work, it’s always important to use your brains.
| A．arise | B．raise | C．arouse | D．rise |
--How are your recent trip to Sichuan?
—I’veneverhad ______ onebefore.
| A．apleasant | B．amorepleasant |
| C．amostpleasant | D．themostpleasant |
Shy people often avoid situationswould force them into close contact with other people．
| A．which | B．where | C．when | D．what |
—How long do you think it will be______man can finally solve the problem of cancer?
—Well，it depends
| A．when | B．until | C．after | D．before |
______ is known to us is that tobacco contains nicotine and other harmful products, so you should give up smoking.
| A．As | B．It | C．What | D．Which |