请教关于语法笔记2007的一道题

Alex2009221733

为神马这句话不用虚拟语气？ 一直搞不懂条件状语从句什么时候需要用虚拟，什么时候不用，请各位牛人赐教
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 it 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
A.     复数those不能指代单数level，因此只能强制指代前句的复数主语emissions，那么，句子变成将
level与emissions相比较，比较对象不对等
B.     正确。
C.    主语应该使用will，而不是would
D.    主语应该使用will，而不是would；复数those没有指代对象
E.     主语应该使用will，而不是would；复数they没有指代对象