GWD14-32求解

Q32:

To develop more accurate population forecasts, demographers have to know a great deal more than now about the social and economic determinants of fertility.

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 economic

答案是D（红色阴影），我不明白为什么选ecnomical而选ecomic，谢谢帮助！

有好心人知道吗？