[求助]GWD-1-32

qwrersaa

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

答案是E，但我不明白C错在哪里？尽量补出谓语动词或助动词不是比E更好吗？

sammen

我选的是D，ECONOMICAL好像是指节约啊，ECONOMIC是经济的，这个问题我还的查查字典，但是我觉得这里的补动词补的没问题啊，如果答案是正确的话，可能是认为应该补HAVE吧，希望牛牛们给解释一下。