16日考试紧急求助2002-10-11等4道语法，谢谢！

0210

11. （         ）over 100 years since the invention of the square-bottomed paper bag.

(A)  Now is

(B)  Now it has

(C)  There is now

(D)  It is now

答案是D。我一直不明白（C）和（D）用法上的区别，王海波笔记上还说过此种情况下优先选择there be

0209

35.Electricity is the phenomenon （associated ）with positively and negatively （particles charged ）of matter （at rest ）and in motion, either （individually） or in great numbers.

答案是C，为什么？我选A为什么不是associating？怎么译？

9705

36.(One of the problems) of United States agriculture that has persisted (during the) 1920’s until the present day is the tendency of farm income to lag (behind) the costs of (production).

答案是B，为什么？

新东方桔色封面新教材练习二十二

31.(In most) cases of epilepsy, cerebral electrical activity, also known as brain waves, (demonstrates) a (characteristically) abnormal (rhythms).

答案是D,改为rhythm。但是B为什么对？主语不是cases吗？

大侠们帮帮忙！谢了！

....最后一题的主语怎么能是cases? cerebral electrical activity 是主语，所以谓语单数正确。

36题B的介词不对，后面是until前面不会是during.可以是from...until

最后两道题前几天解答过，你可以在问题汇总的帖子里按年代找一下，那里总结很全。

第二题答案应该是B，两个词调过来，adj+n 。 associating是主动伴随，但这里主语应该是被动伴随，所以用associated.

第一题不是王海波说的情况。这里后面有个since表完成/持续至今的意思。有三种表达。

It is 20 years since he died.

he died 20years ago.

he has lived there for 20 years.

it可以用来表示时间、天气等等，there be表示的是存在。