Question

我有些不懂得英语题，希望得到大家的帮助，谢谢啦~

1.— There’s someone knocking at the door. Who could _____ be?
— I have no idea.
A. he B. it C. she D. that
为什么答案是B，D为什么不对？
2.At one time we had about eighty people here who did nothing but_____into various family history.
A. researched B. research C. researching D. to research
答案为什么是B，而不是C？
3._______ harder, you would have passed this exam.
A. If you have worked B. If you worked C. Were you to work D. Had you worked
答案为什么是D而不是A？
4.Your hair needs _________. You’d better have it done tomorrow.
A. cut B. cutting C. to cut D. being cut
D选项为什么不对？
5.When _______ to dinner at the White Rose Restaurant, he seemed very happy and accepted the invitation.
A. invited B. inviting C. to be invited D. having invited
为什么C不对呢？

Answer 1

1.因为听见敲门声，你并不知道是男是女，在英语习惯中，用it 代替。接电话也是一样的，通常会说: "who is it?"
2.时态一致。but 前用的是did , 所以but 后应该用researched.
3.这是一个省略句。还原后应该是"if you had worked". 后面跟的是"would have"前面应该用“过去的过去”时态，所以用"have worked "不对。
4、need后要么接不定时，要么接动词原形，不接v.+ing时态
5、when后面不能接不定式。

Answer 2

1,someone你并不知道是男的是女的,所以用it 。 至于that ,我是凭语感。
2 B是动词，C是名词
3这是IF条件句的省略形式，从句有主语了，所以主句用省略
4 主动与被动的关系你还是看一下把
5 独立成份与疑问词冲突。

Answer 3

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