OG12 SC 41

CloverJackier

To develop more zccurate population forecasts,demographers (have to know a great deal more than now about the social and economic) determinants of fertility.

B.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

看了OG的解释  还是没太明白为什么要用虚拟语气   知道B中的ECONOMICAL不正确 但如果换成economic还是不对     为什么这里是一个假设性的说法呢？ 谢谢

logowuyi

OG的解释还有一句话叫 or contrary-to-fact construction，也就是与现实相反。
那这里是说 科学家为了能更精确的预测人口，需要知道更多，也就是说他们现在还没知道很多，与现实相反，所以要用虚拟语气~
我也不知道这样解释对不对~给个参考吧~

williams

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”

supermanlee

我理解would关键是对应过去.过去比较现在.
不只是虚拟的语气.