which在这里是引导非限定性定语从句，which引导非限定性定语从句有2个特点：

　　1. which前面有逗号与其他句子分开。 2. which指的是前面整句话的内容。

　　as也可以引导非限定性定语从句，指的都是一句话的内容。

　　which指一句话的内容只能置于该句之后，而as既可以在后也可以在前。

　　67. _C_ is known to the world， Mark Twain is great American writer.

　　A That B Which C As D It

　　60. In the advanced course students must take performance tests at monthly _B_.

　　A gaps B intervals C length D distance

　　interval n. 间隔(即可指空间间隔，也可指时间间隔)，四级考试中专考时间间隔的概念。

　　interval是固定与介词at搭配的。

　　23. Students or teachers can participate in excursions to lovely beaches around the island at regular _D_.

　　A gaps B rate C length D intervals

　　at regular rate 以规则的速度; at regular interval 以规则的时间间隔;

　　61. Mr. Johnson preferred _A_ heavier work to do.

　　A to be given B to be giving C to have given D having given

　　64. Our company decided to _D_ the contract because a number of the conditions in it had not been met.

　　A destroy B resist C assume D cancel

　　65. She is _C_ a musician than her brother.

　　A much of B much as C more of D more as

　　be of 具有某种性质、品质或特点;

　　66. Having been found guilty， the man was given a severe _B_ by the judge.

　　A service B sentence C crime D crisis

　　sentence n. 判决，判刑; crisis n. 危机; economic crisis 经济危机;

　　68. The residents， _C_ had been damaged by the flood， were given help by the Red Cross.

　　A all their homes B all whose homes C all of whose homes D all of their homes

　　当给出了句子的主语，且后面有两部分谓语动词，这两部分谓语动词之间又没有连接词，

　　时态也不同时，离主语近的谓语动词应为从句的组合成分。

　　69. You can’t afford to let the situation get worse. You must take _D_ to put it right.

　　A decisions B directions C sides D steps

　　take steps 采取措施，采取行动; take measures 采取措施

　　70. Look at the terrible situation I am in! If only I _B_ your advice.

　　A follow B had followed C would follow D have followed

　　if only 如果，要是。..就好了，其后面的句子一定要用虚拟语气。

　　1. 如果if only后面的句子表示与现在或将来的事实相反，这时谓语动词用一般过去时体现虚拟语气。

　　2. 如果if only后面的句子表示与过去的事实相反，这时谓语动词用过去完成时体现虚拟语气。

　　47. If only the committee _D_ the regulations and put them into effect as soon as possible

　　A approve B will approve C can approve D would approve

　　如果if only后面的句子表示与现在或将来的事实相反，这时谓语动词用一般过去时，

　　也可以用would + 动词原形。