Question

问一些高中英语问题2，希望详细解答，谢谢！

1. In our class there are 46 students, of whom half wear glasses.为什么用whom不用who？
2. Left over 什么意思？Left out 什么意思？
3. Most birds find it safe to sleep in the trees, but unless they have eggs or young chicks, they don't use a nest.这里用unless是什么意思，能不能用when？
4. It is almost five years since we saw each other last time.这句中能否用完成时？能用的话是怎样的？
5. It was evening before we reached the little town of Magnolia.能不能用until或者when？为什么？
6. While modeling business is by no means easy to get into, the good model will always be in demand.这里为什么不能用as？
7. Walking in the fields on a March afternoon, he could feel the warmth of spring.
8. Lucy insisted that he was not asleep although I had great difficulty in waking her up.为什么能用although，这个不是只能用在句首吗？
9. As it reported, it is 100 years since Qinghua University was founded.为什么这里用since？用了since前面不应该是has been吗？或者说用has been 也可以吗？
10. However serious a problem you may have, you should gather your courage to face the challenge.为什么不能用what a serious problem？

Answer 1

1.of 后面接的是宾格，所以用whom
2.left over 是剩下，留下 left out 是忽视，不考虑，被遗忘
3.unless是除非的意思，整句话的意思是：大多数的鸟儿发现在树上睡安全，他们不筑巢，除非他们有蛋或有小鸟。应该不可以。
4.