GWD 1-32

JEANINDE

To develop more accurate population forecasts, demographers have to know a great deal more than now about the social and economic determinants of fertility.

have to know a great deal more than now about the social and economic

have to know a great deal more than they do now about the social and economical

would have to know a great deal more than they do now about the social and economical

would have to know a great deal more than they do now about the social and economic

would have to know a great deal more than now about the social and economical

   

Why not B?

calculus

why not A?

lfeng08908

在这个句子中没有可混淆的成分，所以无需补出they do，只需than now。既然是比较，就应有比较的双方，本句在比较将来与now，所以A中，have to know 与now同时态，这就不合适了。不知是否有道理，请考虑。

seven

But why E?

How can E be the answer with "economical" in it?

bryan0806

我覺得 would在這邊有表示 猜測不確定性 像是if的結果句的作用

既然用would 所以後面補出 they do 以表明時態 now  

如果時態一樣我覺得應該they do 可以省 像A這樣

BCE的economical 意思不同  還請指教

bluewindow2008

困惑中......

是不是因为是推测才必须用would，不用补出they do也很清楚啊？生孩子当然是社会和经济(economical)上的决定因素啦......

trojanlove

economical:节约的, 经济的

economic:经济(上)的, 产供销的, 经济学的

两者有区别阿

天使与海豚

困惑中，忘高人指点。。

serenaluo

顶！

我不明白为什么这里要用WOULD HAVE。请指教。

hannah1112

我觉得would 表明的是一种虚拟假设，就是说，To develop more accurate population forecasts,那么demographers就应该怎么怎么样，所以用would have to 更好，但是我不明白为什么用economical 而不是economic, economic才能和social对应啊？？？？

请高人指点？！