Question

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 economic

Answer 1

The correct option is D would have to know a great deal more than they do now about the social and economic

The sentence implies a hypothetical situation - the demographers might or might not ever have enough data to develop accurate forecasts. This requires the subjunctive 'would have to know' and not the imperative 'have to know'. Thus,options A, B are eliminated. Focusing on 'than now' and 'they do now'. 'Than now' is incorrect. The comparison is between what they know now and what they would know then. They would have to know more than they 'do now' is the correct one. This discards E. Also, 'economical' implies money saving and the sentence requires the large scale reference that the use of 'economic' implies. "Economical" is illogical here. This eliminates C. Thus option D is the correct choice.