GWD1-32

1. have to know a great deal more than now about the social and economic
2. have to know a great deal more than they do now about the social and economical
3. would have to know a great deal more than they do now about the social and economical
4. would have to know a great deal more than they do now about the social and economic
5. would have to know a great deal more than now about the social and economical

The answer is E.          

 But,  1. 为什么是"would have to"而非"have to"?

         2. 为什么是"than now"而非"than they do now"?

         3. 为什么是"economical"而非"economic"?

请大家指教，多谢了！

是不是我的问题太简单了，所以才没人回答？

这是我第一次来这里问问题，因为周围找不到战友，所以有问题只能到这里麻烦大家，希望大家能帮助我解决问题。谢谢！

I just searched "讨论汇总" and found that the answer should be D.

Thanks!