OG12-41

elsachialee

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
答案D
og解析说 conditional verb is needed.
这里是不是一定要用would呢？
我觉得好像也不是那么硬性的错误吧~
谢谢大家帮忙

-- by 会员 liz_summer (2010/7/25 17:22:41)

would have to know 和 have to know, 应该在这个句子里面不是硬性的错误，就和你说的样子。
用了would have to know多了虚拟的感觉，demographers would have to know (...)about the social and economic determinants of fertility, if demographers had developed more accurate population forecasts. 言下之意，就是现在不知道这个到底有没有去develop。
如果换成了have to know，就是是当下真的要发生的事情。两个语态只是稍微改了句子的意思，不是硬伤。


选项A不正确，是因为必须要补出 they do。我的理解是前后动词前的成分不同。前面有一个have to，所以后面补出they do，意思上面更加明了。


correct me if i am wrong