GWD－24－41

If current trends continue, by the year 2010 carbon emissions in the United States
            will soar to a level more than one-third higher than were those in 1990, according to official projections.

A.      will soar to a level more than one-third higher than were those

B.      will soar to a level more than one-third higher than that

C.      would soar to a level more than one-third higher than is was

D.      would soar to a level more than one-third higher than those

E.       would soar to a level more than one-third higher than they were

答案是B没有问题，我想问下这个句子的条件从句使用一般现在时，所以是否主句一定不能用虚拟语态，尽管主句所描述的事情是预测当中没有实际发生的。(我自己记得好像是有这么一条语法规定的，就是孤独的if从句用虚拟语气表示条件，但是不能够从句一般时，主句用虚拟。想和大家确认一下)

如果CDE中有一个改为would soar to a level more than one-third higher than that是否可以成为正确选项呢？

谢谢

我觉得虚拟的使用在于作者的态度，态度上是“实际上一定不会发生，但确实这么假设”

而此题，作者的意思就是一个预测，另外提一下，一般将来时，will，表示的事情都没发生，几乎都是预测。

只要这个预测跟作者自己的意思没有冲突就不用虚拟。