This is ______ difficult problem that few students can work it out.
| A．so | B．so a | C．such | D．such a |
Tom had tothe invitation to the party last weekend because he was too busy.
| A． | turn in | B． | turn down |
| C． | turn over | D． | turn to |
Despite the previous rounds of talks, no agreement______ so far by the two sides.
| A．has been reached | B．was reached |
| C．will reach | D．will have reached |
______ for two days, Steve managed to finish his report on schedule.
| A．To work | B．Worked |
| C．To be working | D．Having worked |
I ______ have worried before I came to the new school, for my classmates here are very friendly to me.
| A．mightn’t | B．mustn’t |
| C．needn’t | D．couldn’t |
Jane can’t attend the meeting at 3 o’clock this afternoon because she ______ a class at that time.
| A．will teach | B．would teach |
| C．has taught | D．will be teaching |