21. until then, his family _d_ from him for six months.
a didn't hear b hasn't been hearing c hasn't heard d hadn't heard
until then 直到那时。hear from sb. 收到某人的来信，得到某人的消息。
22. the conference _b_ a full week by the time it ends.
a must have lasted b will have lasted c would last d has lasted
见到介词by引导的时间状语，谓语动词就应是完成时态。
24. physics is _b_ to the science which was called natural philosophy in history.
a alike b equivalent c likely d uniform
be alike to sb. 对于某人来说均是一样的。be equivalent to 相当于。
all tastes are alike to him. 所有味道对他来说都一样。
27. the new appointment of our president _a_ from the very beginning of next semester.
a takes effect b takes part c takes place d takes turns
semester n. 学期；president n. 大学校长；take effect 生效，发生效力；
take part in 参与，参加；take place=happen 发生；takes turn to do sth. 轮流做某事。
28. the president made a _a_ speech at the opening ceremony of the sports meeting, which encouraged the sportsmen greatly.
a vigorous b tedious c flat d harsh
ceremony n. 典礼，仪式；表达在某个典礼上介词用at。vigorous adj. 强劲有力的，强有力的。
harsh adj. 刺耳的，令人不愉快的；flat adj. 平淡无奇的；tedious adj. 冗长无聊的。
29. it is useful to be able to predict the extent _c_ which a price change will affect supply and demand. [extent to]
a from b with c to d for
30. finding a job in such a big company has always been _d_ his wildest dreams.
a under b over c above d beyond
beyond one’s wildest dreams 做梦也想不到。
31. it is not easy to learn english well, but if you _c_, you will succeed in the end.
a hang up b hang about c hang on d hang onto
hang on 坚持，继续下去。
32. it is reported that _c_ adopted children want to know who their natural parents are.
a the most b most of c most d the most of
most 单独出现的时候有两种词性要考虑：1 adv. 非常；2 adj. 大多数的。
the most后面加多音节的形容词或副词构成该句的最高级。
most of + 名词，表示这些名词中的大多数。make the most of 充分利用。
34. _d_ before we depart the day after tomorrow, we should have a wonderful dinner party. [were they to arrive=if they were to arrive]
a had they arrived b would they arrive c were they arriving d were they to arrive
35. the strong storm did a lot of damage to the coastal villages: several fishing boats were _a_ and many houses collapsed.
a wrecked b spoiled c torn d injured
collapse vi. 倒塌，坍塌；wreck vt. （船只）遭到破坏。
torn原形是tear，n. 眼泪，vt. 撕裂，撕开。
37. as _b_ announced in today's papers, the shanghai export commodities fair is also open on sundays.
a being b is c to be d been
注意两个 非限定性定语从句的引导词 ：as, which。
which在做非限定性定语从句引导词时有两个特点：
1 which前要有逗号与前面句子分开；2 which引导非限定性定语从句指的是前面整句话的内容。
只要引导非限定性定语从句as和which都指一句话内容，区别在于which只能放在它所指那句话的后面，而as可以在前面也可以在后面。
38. you see the lightning _a_ it happens, but you hear the thunder later.
a the instant b for an instant c on the instant d in an instant
the instant=as soon as 一…就…
39. the manager lost his _b_ just because his secretary was ten minutes late.
a mood b temper c mind d passion
lose one’s temper 发脾气。
40. great as newton was, many of his ideas _c_ today and are being modified by the work of scientists of our time.
a are to challenge b may be challenged c have been challenged d are challenging
as表示“尽管”时引导从句，从句中的表语可以放在引导词之前构成部分倒装。
41. please be careful when you are drinking coffee in case you _d_ the new carpet.
a crash b pollute c spot d stain
pollute vt. 污染；spot n. 地点，场所，斑点，污点；v. 使…上有斑点、污点。
spotted dog 斑点狗。stain v. 弄脏，玷污，染色。
59. the tomato juice left brown _a_ on the front of my jacket.
a spot b point c track d trace
42. i'd rather read than watch television; the programs seem _b_ all the time.
a to get worse b to be getting worse c to have got worse d getting worse
all the time 始终，一直。
43. convenience foods which are already prepared for cooking are _d_ in grocery stores.
a ready b approachable c probable d available
convenience foods 方便食品；instant coffee/noodle 速容咖啡/速食面。
ready adj. 准备好的；approachable adj. 可接近的，平易近人的，亲切的。
probable adj. 可能的；available adj. 可获得的，可利用的，可支配的。
44. when i caught him _a_ i stopped buying things there and started dealing with another shop.
a cheating b cheat c to cheat d to be cheating
45. it is important that enough money _a_ to fund the project.
a be collected b must be collected c was collected d can be collected
46. some old people don't like pop songs because they can't _c_ so much noise.
a resist b sustain c tolerate d undergo
tolerate vt. 忍受，容忍；undergo vt. 经历，遭受。
48. _c_ one time, manchester was the home of the most productive cotton mills in the world. [at one time 曾经，一度]
a on b by c at d of
49. _a_ it or not, his discovery has created a stir in scientific circles.
a believe b to believe c believing d believed
believe it or not 信不信由你。creat a stir 引起轰动。
50. mr. morgan can be very sad _c_, though in public he is extremely cheerful.
a by himself b in person c in private d as individual
in public 在公众面前；in private 私下单独一个人的时候。