GWD-1-Q32请高人指点

colette

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

答案给的E，有人选B，我怎么觉得应该是A呢？

这里考的三个点：时态，比较和形容词，应该重点在第一和第三吧？原来的答案E也没有考虑比较的问题。

running

economical 通常指节约的 not wasteful or extravagant，也可以=economic;  我倾向于选择social and economical，至少形式上对称。than 后面补充完整应该是than they now know, 不应该是than they know now, 因为后面紧跟着about.    would have 是虚拟语气而已。