OG12 SC 41

JUNO1031

41.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

我想请问NN的是这里为什么要加they do 说比较的是人类统计学家现在在知道的知识，不能能和现有的知识比较，不是也是一样是虚拟的情况？

不胜感激

wanghonglia

貌似是lz的理解有些偏差吧。。。
og的意思是比较的对象要对等，would have to know a great deal只能和知道的内容比较，而不能和表示时间的now来比较。

hanshipeng

The comparison is not parallel.

If you omit they do, the comparison will be THEY KNOW A GREAT DEAL MORE(V+N) than NOW(ADV), apparently it is wrong.

JUNO1031

不是说比较在省略中只要把比较的核心指出来就可以的吗？这里比较的是现有的知识和需要的知识 ，那么不同的不是只有时间的不同？这样只留下now不是可以吗？

charles1992

这个句子比较的是what they know now 和what they know in the future. a great deal  不是跟they know 一体的，而是跟more 一体的，是 a great deal more than ,翻译为 比。。。多得多。如果要省略than 后面的内容，more than 前后必须有相同的部分，而句子里than 后面和前面并没有除了know以外相同的部分呀～就把know 替换为do了。