求 GWD1 Q32 语法

今天做了一套GWD 对其中一道语法题的答案有疑意, 特此跟大家讨论一下. 题目如下:

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 economical
我选A, 答案给的是E. 首先,我没发现A 有什么不对; 其次,从词的意思上说,应该是 economic determinants, economical 是节俭的意思,应该排除B, C, E.最后,也没有什么特别的理由,把have to 改成would have to, 也就是D答案.

实在不明白,请赐教!! 谢谢!! 

tip: 楼主，置顶贴中有讨论。

demographer，n，人口统计学家

economical，节约的，经济的（不合本题意）

economic，经济上的，经济学的

A，比较对象不匹配，主要是没有用would

B、C、E，economical不合题意

D is the best

本题的would的用法：used when talking about a possible situation that you imagine or want to happen.

这里是两种情况的完整比较，主谓状的完全比较，因为谓语和状语都不相同，所以这里全部没有省略。

thank you very much!!!