When I tried to find _________that prevented so many people from taking part in the program, it seemed to me that there were two main reasons.
| A．why it did | B．that it did |
| C．what it was | D．why it was |
The surface of the table ______ smooth enough．
| A．hash’t felt | B．isn’t feeling | C．doesn’t feel | D．isn’t felt |
一Why didn’t you try your best to get on the bus?
一I tried to，but ______ I could，it started moving．
| A．until | B．when | C．before | D．after |
You seem to have a ready—made answer _______ I ask you a question．
| A．however | B．whatever | C．whichever | D．whenever |
一You have made great progress in your studies of English，haven’t you?
一Yes，but much _______ ．‘
| A．remains to do | B．is remained to do |
| C．remains to be done | D．is remained to be done |
________ to overcome the difficulty，he works day and night．
| A．Determined | B．Determining |
| C．To determine | D．To be determined |