Help Gwd-1-32

nbnhjf

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.

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

Can you give me some detail explanation for choosing have to or would have to ?

Thank you

sammen

从now看，我觉得前面的是过去的，排除AB，，在根据对称，排除E，最后根据economic和economical的意思，选C。