求助PREP语法，第二部分187题（GWD-1-Q32)

zqlzql1122

题目如下：
187. (GWD-1-Q32)
To develop more accurate population forecasts, demographers have to know a great deal more than now about the social and economic determinants of fertility.
A. have to know a great deal more than now about the social and economic
B. have to know a great deal more than they do now about the social and economical
C. would have to know a great deal more than they do now about the social and economical
D. would have to know a great deal more than they do now about the social and economic
E. would have to know a great deal more than now about the social and economic


这里有关比较的问题搞不清了，论坛上语法资料上是这样的：
对主谓宾全的句型
状语比较： A do sth than usual/everbefore/people expected(直接加状语）


所以这里难道不是than后面直接加NOW嘛？
求大神解答！

zqlzql1122

渣渣求大神帮助

Yolanda_ljc

楼主，今天无意中翻到你的帖子，在我看了很多帖子之后好像明白原因了，下面是我的理解，欢迎一起讨论

你给的状语比较结构是：A do sth than usual/everbefore/people expected(直接加状语）。这和GWD-1-Q32这道题的选项是有区别的，选项的比较结构是A do sth than usual/everbefore/people expected+about....determinants
因为than后面存在的红色部分，所以than后不能直接加not：红色部分(宾语）相当于一个提示，即than后要出现完整的主谓宾结构
主谓宾 than  主谓宾状   
而A和E选项是 主谓状（1） than  宾状（2） ，这是不符合语法要求的，宾语的省略要在（1）主句处省略而不能在从句处省略。  所以如果A和E选项这部分改成   demographers would have to know a great deal more about the social and economic determinants of fertility than (they do ) now就对了。