我建议选择题用排除法：
1. that引导定语从句,并且在句中作主语,那么从句就不应该再出现主语,在A,B,C三个答案中都有they,因此,选D．
13. D．在one of +名词（复数）＋定语从句这个节后中,定语从句的谓语动词的数,应由这个定语从句所修饰的先行词的数来决定；如果one前面有the only, the, the very等非常明确的限定词时,我们说定语从句修饰的是one；如果没有,我们可以确定,这个定语从句修饰的是one of + 名词（复数）中的名词（复数）,因此,例如：
This if one of the the rooms that were damaged in the fire. (that引导定语从句,从句的谓语动词用复数were)
He is the only one of the boys who is going to visit Japan. (who引导定语从句,从句的谓语动词用单数is going to ,因为one前有the only修饰)
18. We will be shown around the city: schools, museums and some other places, __C_ other visitors seldom go.
A. what B. which C. where D. when
在个句子中,先把A. what去掉,因为,这个词不能引导定语从句．
剩下的三个词,which指物,在句中作主语或宾语；where表示地点,when表示时间．我们看定语从句：other visitors seldom go.这句中,other visitors 作主语,go是不及物动词,因此是不能接宾语的,所以,我们把which也去掉,前面的places表地点,我们选where
20. _B______ has been announced, we shall have our final exams next month.
A. That B. As C. It D. What
这四个答案中,只有as才可以引导非限制性定语从句,意为：正如.,像.;从句可放在句首,中,或句末（一般的定语从句,都是直接放在先行词后面,只有这个as例外）．
23. Helen was much kinder to her youngest son than to the others, __D____, of course, made the others envy him.
A. who B. that C. what D. which
这句话,是非限制性定语从句,因此,把B, C去掉,____made the others envy him意为,这件事,使其他人非常嫉妒他．who指人,which 指物,因此,选D.
26. Anyway, that evening, __D_ I'll tell you more about later, I ended up staying at Rachel’s place.
A. when B. where C. what D. which
先把C去掉,因为这不表示地点,把B也去掉；____I'll tell you more about later．这句话中,I作主语,tell sb sth告诉某人某事, tell sb about 告诉某人有关某事的情况,later adv. 随后；稍后；后来,一般介词后面接名词代词或动名词,about后,没有宾语,因此选关系代词,which
30. There are two buildings, _D__ stands nearly a hundred feet high .
A．the larger B．the larger of them
C．the larger one that D．the larger of which
the +形容词比较级表示两个人或物中比较...的一个．stands为动词,这个句子中需要主语,the larger one of which = the larger one of the two buildings, 在介词后面,指物,用关系代词which.
36. The journey around the world took the old sailor nine months, _B___ the sailing time was 226 days.
A. of which B. during which C. from which D. for which
引导定语从句除了可以用关系代词或关系副词外,还有一种是：介词＋关系代词（that除外）,那么,在of, during, from, for四个介词中,在表示时间的时候,一般是during, from, for这三个介词,during在．．．期间；from从．．．；for表示时间长度,因此,选during表示,在...期间．
39. A fast food restaurant is the place __B__, just as the name suggests, eating is performed quickly.
A. which B. where C. there D. what
这句话分开看：A fast food restaurant is the place where eating is performed quickly.先行词是the place,先把C,D去掉,我们就要考虑用where,但是,我们还要看,引导定语从句的引导词,在句子中做什么成分,如果作主语或宾语,我们就不能用where,而这个句子where eating is performed quickly.(eating是动名词作主语,is performed被动语态,也就是说,这就话中可以没有宾语（因为,在被动语态中,是主动语态的宾语做了被动语态的主语）),因此,选B．（前面的句子,是不是应该是：just as the same suggests）
44. Last month, part of Southeast Asia was stuck by floods, from ___B____ effects the people are still suffering.
A. that B. whose C. those D. what
先将C,D去掉,from 是介词,在介词后面不能用that引导定语从句, 因此,选B．
47. Frank’s dream was to have his own shop_B_ to produce the workings of his own hands.
A．that B．in which C．by which D．how
这句话有问题
48. The schools themselves admit that not all children will be successful in the jobs __D___ they are being trained.
A．in that B．for that C．in which D．for which
train... for ...为...而训练,先把A, B去掉,根据前面的词组,选D．
49. The way he did it was different ___C__we were used to.
A．in which B．in what C．from what D．from which
be different from与...不同．先将B,C去掉,根据词组选D．
50. I walked in our garden, _C__ Tom and Jim were tying a big sign onto one of the trees.
A．which B．when C．where D．that
先将D去掉,that不能引导非限制性定语从句．这句定语从句的先行词为in our garden 中的garden,因此,将B去掉；在A,C两个选项中,去掉A,因为,which 在句中作主语或宾语,但是,后面的从句不缺这两个部分,因此,选C．
51. — Did Jack come back early last night?
— Yes. It was not yet eight o’clock __B___ he arrived home.
A．before B．when C．that D．until
这句话的意思是：当他到家时已经是八点了．因此,选B．
54. Jim passed the driving test, __A__ surprised everybody in the office. (2005浙江)
A. which B. that C. this D. it
这是非限制性定语从句,在四个答案中只有A可以引导此类句型．