问题 这里是否少了一个冠词

... after doctors completed a 20-hour operation _______ one-year-old twins at the head.A. to separate B. to have separated 老师，您好。题目中one-year-old twins到底指多少对双胞胎？和语境融洽吗？如果不融洽，应该如何修改呢？您的看法是什么？为什么？

问题 the fact引出的从句中一般现在时是否可用现在完成时替代？

Our society would be better off but for the fact that the economy ______ by the current global financial crisis.A. had been affected        B. were affectedC. should be affected        D. is affected这道题目答案是...

话题 of what can be

话题 be of good quality

话题 of与后面词的关系

话题 be of doing sth

话题 an entire flock of

话题 分词和none of us

话题 be made up of

话题 be on alert of

话题 as in all of

话题 coming-of-age

话题 that of general unreserve

话题 allocentric frame of reference

话题 growing minority of academics