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 答案D og解析说 conditional verb is needed. 这里是不是一定要用would呢? 我觉得好像也不是那么硬性的错误吧~ 谢谢大家帮忙
我觉得这边用虚拟语气是为了强调这些人必须要懂的比现在多很多才能达到...的目的。未来和现实相反,OG中说“because in order to more accurately predict population, demographers would have to know more than they presently know”