12.The woman will never forget the day ______ they first met.
A.that B.on which C.on that D.which
什么时候用which，什么时候用on which
13.In the dark street ,there wasn’t a single person _______ she could turn for help .
A.that B.who C.from whom D.to whom
为什么选D，不选其它。
23.I felt very tired for a long walk .Do you mind _______?
A.if I sit here for a moment B.if my sitting here for a moment
C.if I will sit here for a moment D.I sitting here for a moment
为什么选A，不选其它。
24.All living things _______ ,couldn’t live without air or water .
A. no matter what the animals or plants
B. even if animals and plants
C.whether they are animals or plants
D.not only animals but also or plants
为什么选C，不选其它。

12. 正确答案：B. on which

the day -- 那天。 明确的某一天，要用介词 on 。而介词之后，只能用 which 。

13. 正确答案：D. to whom 。

turn to someone for help 求助于某人 。

23. 正确答案：A. if I sit here for a monent

即： If I sit here for a monent, do you mind?

B. if my sitting here for a monent 若去掉 if , 则也是正确答案。即： Do you mind my sitting here for a monent? my sitting 动名词作 mind 的宾语。 C. if I will sit here for a monent 多了个 will 。条件从句的将来时，要用一般现在时。
D. I sitting here for a monent 中，I 改为 my 也是正确答案。

24. 正确答案：C. whether they are animals or plants

A. no mater what... or... B.even if... D.not only...but also... 引导的都应该是句子。但都不是。