请教几道语法题～～～～

tiffanybonneUID: 2138478

1.Algae have been an extremely important link in the food chain after the beginning of life on Earth as we know it


2.Lawrence Robert Klein received the 1980 Nobel Prize in economics for pioneering the useful of computers to forecast economic activity
答案Ｃ
为什么D中activity不用复数?

３．14. _____ to the reproductive rates of other small mammals, that of the bat is
very low indeed.
(A) Compared
(B) It is compared
(C) To be comparing
(D) Have compared

答案Ａ．为什么Ｂ不对？

谢谢先～

MrMosquitoUID: 204833

2. OF 做定语前面肯定是用名词的.后面的ACTIVITY那就只能看做单数,作为总称了吧.

wuyongboUID: 2119636

1.after 改成since
3.第一个逗号之前时状语，逻辑主语为that,如果选B，一句话包括两个单句，不符合语法规则

tiffanybonneUID: 2138478

Originally posted by wuyongbo at 2005-11-16 18:38
1.after 改成since

我想知道为什么这个改?
按AFTER理解内容也说的通

goodenoughUID: 2149577

1前面是have been,后面用表一段时间的since
2use名词
3做状语