The book was written in 1946, ____ the education system has witnessed great charges.
| A．when | B．during which | C．since then | D．since when |
How long do you think _________ the computer company launches a new model?
| A．it will be before | B．will it be until | C．will it be when | D．it will be that |
Miss Li _ as a secretary for five years in the company, and now she is general manager of it.
| A．serves | B．served | C．had served | D．has served |
A warm thought suddenly came to me _______ I might substitute the hero to buy some flowers for his mother’s 60th birthday. 
| A．if | B．when | C．that | D．which |
Though a typhoon is on the way, people are still looking forward _____ the outdoor concert by the pop singer.
| A．to canceling | B．not to canceling | C．not to cancel | D．to not canceling |
－Mary, how did your Math test go?
－I had thought I _________, but in fact I came in the top 10% in my class.
| A．should have failed | B．couldn’t have failed |
| C．might have failed | D．shouldn’t have failed |