回答不论先来后到，只按精彩度采纳答案~
D 1. The problem ______ has been completely settled.
A. which you thought B. that you thought
C. about which you thought it D. that you thought about
（是不是因为这个不用介词提前啊，哪种的介词不用提前啊）
B 2. Every minute ______ full use of to study our lessons will do our students good.
A. which makes B. that is made C. that made D. what is made
（为什么不选A…像类似Every，Each的在定语从句中选关系词有什么特别要求吗）
C 3. Will it be two months ______ we can get another one?
A. that B. when C. before D. in which
（完全不明白…）

D 4.Water power stations are built ______ big water falls.
A. which are B. which has C. where there have D. where there are
（C为什么不对呢）
D 5.The direction ______ a force acts can be changed.
A. how B. which C. towards D.×
（为什么B不对）
D 6.In the end she decided to sell the house ______ windows were almost broken.
A. which B. that C. of which D. whose
（C为什么不对）
B 7.That ______ you lent me wasn’t _____ I wanted.
A. that; all B. which; all C. that; what D. which; that

（又完全不懂）

D 8.Each time ______ they met, they would talk long hours together.
A. during B. which C. where D.×
（Each time 貌似有什么特别，除了不填还能填什么呢）

A 9.On the desk ______ a Chinese brush ______ he had made drawing.
A. lay; with which B. lies; by which C. laid; in which D. lay; on which
（不明白为什么倒装了的lay要用原型）
仔细点啊我可是很仔细的打得~

1. 介词提不提前没有绝对规定，一般是习惯问题：限制性定语从句中，把介词提前只见于非常正式的书面语中，一般把介词放在后面，并且省略关系代词；在非限制性定语从句中，书面语中一般是把介词提前。对于动词与介词的固定搭配词组，把介词提前会把这种固定搭配割裂开来，显得不自然，所以一般不提前。
这题的答案选择与介词替补提前无关。
A,B, thought 后少了介词about,不通。 C.it 多余。

2。A不对，因为必须用被动态。时间是被人利用的。

3。不是定语从句。before在这里是连词。
It will be...before+从句 是一种固定句型，意思是"还要...时间才能..."。

4。固定搭配是there be(is,are,were...), there have是错的。

5.The direction ______ a force acts can be changed。 意思是"力作用的方向可以改变"。 正常来说，The direction 之前应该有介词 in，即"在...方向",所以正确答案可选 in which, 但是在限制性定语从句中，关系代词that可以表示in/for/on which的意思，而且这种情况that可以省略，所以D对。B少了in,所以不对。

6. 如果选C，那么windows 前还得有个the, 所以不对。

7. 个人认为只有D不对。

8.Each time作整个句子的状语，跟ever day, last sunday等一样，前面不要介词。they met又是修饰 each time的定语从句，答案选择的理由同5.

9. lay是lie(躺)的过去式,不是原型。这里动词只能用不及物动词lie(躺)，不能用及物动词lay(放).