To develop more accurate population forecasts

[agarbattis]

Can you pl explain the answer for this Qn

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

[chandak_anand]

Should be D. What is the Official Answer?

[yashesha]

i go with D..

[jadugar]

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

There are three errors in the incorrect sentences:
1. The sentence should use future perfect tense since the two events are occuring in sequence in future. Sentence should use "would have" and not "have". Options A, B are ruled out; options C, D, E satisfy.
2. Word economic and economical are not same although both of them are adjectives. This is altered intent case. Options B, C, E are ruled out; options A, D satisfy.
3. Faulty comparison of time and knowledge. "to know" is compared to "now", while it should have been "they know now" to "what they would know". Options A, E are ruled out; options B, C, D satisfy.

So only option D satify.

[ontheway]

I don't think " would have" should be preferred over "have" in this sentence. Normally "would have" should be used to refer future prospect of any past event. I think present tense is enough to retain the meaning of the sentence.
Only A & D use word "economic", making them viable options while others using word "economical" that changes meaning of the sentence.
A compares knowledge to time (now) therefore faulty.
Only option left is D.

[jadugar]

I don't think " would have" should be preferred over "have" in this sentence. Normally "would have" should be used to refer future prospect of any past event. I think present tense is enough to retain the meaning of the sentence.

I think you are right. I drop my argument 1.

[anilmanu]

I pick D too

[prreeet]

D for me as well....

[lesfeaves]

IMO A

As would is used to describe future event of past event and here both the events are in future.

[dv_dheeraj]

i think usage of would is warranted as it is a conditional statement.