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FIDELISCARE

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

joe11

You can find answers here:

http://forum.chasedream.com/dispbbs.asp?BoardID=23&ID=56794