When I try to understand ____ that prevents so many Americans from being as happy as one might expect, it seems to me that there are two causes.
| A．why does it | B．what does it | C．what it is | D．why it is |
I felt somewhat disappointed and was about to leave _____ something occurred which attracted my attention.
| A．unless | B．until | C．when | D．while |
Led by the Party, ___ we fight firmly with one heart and one mind, depending upon science, we will surely defeat SARS.
| A．in case | B．so far as | C．even if | D．so long as |
—I’d like to invite you to my new house next weekend.
—Thank you, but ____ I’ll have time I’m not sure at the moment.
| A．when | B．as | C．in case | D．unless |
—How long do you suppose it is ____ he? —No more than half a week.
| A．when | B．before | C．after | D．since |
___ China’s reform（改革）and opening up in fate 1978, its quick development has aroused worldwide attention.
| A．When | B．As | C．While | D．Since |