46. when he arrived， he found _c_ the aged and the sick at home.
a nothing but b none other c none but d no other than
形容词前加the表示一类人。 none but 只有，仅有。
47. the pressure _b_ causes americans to be energetic， but it also puts them under a constant emotional strain.
a competing b to compete c to be competed d having competed
the right to vote 选举权。 动词不定式作后置定语要用主动形式。
the pressure to compete 竞争的压力。
49. as teachers we should concern ourselves with what is said， not what we think _c_.
a have to be said b must say c ought to be said d need to say
50. once environmental damage _a_， it takes many years for the system to recover.
a is done b is to do c does d has done
51. studies show that the things that contribute most to a sense of happiness cannot be bought， _b_ a good family life， friendship and work satisfaction.
a as for b such as c in case of d in view of
contribute to 对…做出贡献。
52. he will agree to do what you require _d_ him.
a for b from c to d of
require sth. of sb. 要求某人做某事。
53. the mere fact _a_ most people believe nuclear war would be madness does not mean that it will not occur.
a that b which c what d why
fact后面要加同位语从句。
54. john seems nice person. _c_， i don't trust him.
a even though b therefore c even so d though
even so 即便如此，尽管如此。
55. i don't think it advisable that tom _a_ to the job since he has no experience.
a be assigned b will be assigned c is assigned d has been assigned
advisable后面加句子要用虚拟语气，形式为：（should）+ 动词原形。
56. _d_， a man who expresses himself effectively is sure to succeed more rapidly than a man whose command of language is poor.
a other things to be equal b were other things equal
c to be equal to other things d other things being equal
b项如果不省略if应为：if other things were equal
如果从句用虚拟语气，主句也必须用虚拟语气形式。
other things being equal 在这里是独立主格做条件状语。