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9.You have made a few mistakes in your composition but______,it’s well written.

A.first of all            B.on the whole

C.on the other hand       D.so far

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8.Most of the students in our class like to read China Daily,which________every day.

A.comes out           B.comes up

C.come across          D.comes about

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7.-How do you find the football match between England  and Italy?

-There is nothing special-it is only________.

A.average             B.usual

C.typical              D.normal

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6.Quantities of water________for cooling in the only one of the plants that________steel.

A.has been needed;produces

B.are needed;produces

C.is needed;produce

D.have been needed;produce

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5.-She should not have done that sort of thing.

-Whatever she did was reasonable,________to what  you have done.Besides,it’s none of your business.Get down to________your lessons.

A.compared;doing          B.comparing;doing

C.compared;do        D.comparing;do

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4.________for her,Chen Zhong,the last champion,had no chance to take part in the finals.

A.Luckily              B.Unfortunately

C.Obviously            D.Absolutely

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3.-Lucy looks blue today.

-Yes,but I don’t know what it is________makes her  so upset.

A.as                  B.what

C.that                 D.which

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2.I________at my watch and was surprised to see that it was nearly midnight.

A.glanced              B.observed

C.glared              D.stared

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1.They are ready to take________action regardless of________consequence.

A./;a       B.the;the

C./;the               D.an;the

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例5  用分子量为43的烷基取代甲苯苯环上的一个氢原子所得的芳香烃产物数目为(   )

A、3种   B、4种   C、5种   D、6种

解析:烷基的通式为-CnH2n+1,M=43,由12n+2n+1=43。解得n=3,C3H7-烃基可能有两种:

CH3-CH2-CH-和         

它们可分别取代苯环上邻、间、对位上的氢原子。甲苯有三个不对称位置,        

故两种不同的烃基取代苯环上的一个氢原子,得到的同分异构体数目为2×3=6(种)。

答案:D

例6  1,2,3-三苯基环丙烷的3个苯基可以分布在环丙烷平面的上下,因此有如下2个异构体。

[是苯基,环用键线表示,C、H原子都未画出  ]

据此,可判断1,2,3,4,5-五氯环戊烷(假定五个碳原子也处于同一平面上)的异构体数是(  )

A、4    B、5     C、6      D、7

解析:从1,2,3-三苯基环丙烷的结构可以看出苯环可处于平面的上方或下方。可以得出:

①氯全部在面上(或面下),1种

②4个氯在面上,1个氯在面下,1种。

③3个氯在面上,2个氯在面下,2种。

答案:A

变形题

邻甲基苯甲酸              有多种同分异构体,其中属于酯类,且分子结构中有

甲基和苯环的异构体有(  )

A、2种    B、3种   C、4种    D、5种

解析;据题目要求,同学们要注意苯环不能拆,那么只能改变苯环上的两个取代基。一般来讲,大家很容易看出-COOH和-CH3组合成-COOCH3,而容易忽略-COOH与-OOCH的区别,前者应为羧酸,而后者为甲酸某酯,故有异构体:

答案:D

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