比较中的省略主谓问题

kilaspring

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

[url=](E) would have to know a great deal more than now about the social and economic[/url]

为什么E错了，这道题对于时间状语的比较，应该可以省略主谓吧？
比如下面的例子：

I walk as fast now as [I walked] when I was a child.
这里的i walked就可以省略。

jhanas

我本来以为选B的，一看economical，觉得原来错了。可是这道题目为什么用would have to know.....直接have to know也可以啊。

jhanas

。。。。。。。。。。。

lily510

省略是在不引起歧义的情况下做出的。你的例子没有歧义，可是og省略后，很明显引起双方比较不对称的歧义，一方是demographers的knowledge，另一方是时间now。此处想要对比的是demographers know 的 a great deal ，选项D would have to know  a great deal  more than they do now about the social and economic
中的do 就代指了 know  a great deal  ，所以不能去掉they do
个人理解。

lily510

省略是在不引起歧义的情况下做出的。你的例子没有歧义，可是og省略后，很明显引起双方比较不对称的歧义，一方是demographers的knowledge，另一方是时间now。此处想要对比的是demographers know 的 a great deal ，选项D would have to know  a great deal  more than they do now about the social and economic
中的do 就代指了 know  a great deal  ，所以不能去掉they do
个人理解。