To develop more accurate population forecasts, demographers have to know a great deal more than now about the social and economic determinants of fertility.
A.have to know a great deal more than now about the social and economic
B.have to know a great deal more than they do now about the social and economical
C.would have to know a great deal more than they do now about the social and economical
D.would have to know a great deal more than they do now about the social and economic
E.would have to know a great deal more than now about the social and economical
key：D 想问一下为什么不能用状语比较？就是直接用now 和以前的比较 就是A选项 作者: 九珍豆腐 时间: 2011-8-10 20:31
than now about 所以have to 表示现在和现在比 句子意思应该是将来和现在比 所以要加would