求助各位高人为小弟指点GWD上的一道考题！！

mcyuyu

GWD最新题1套的32题：正确答案是啥and为啥？主句是否要加would?  这里的have是不是助动词？ 比较句than后是否加do？

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

   

蓝夕叶子

【发帖必读】 GMAT语法区版规   [ 1 2 ]