If current trends continue, by the year 2010 carbon emissions in the United States

(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

上述是官方解释，那么请问，A是否后面改为单数（than was it），C用了will（than it was），就都成立呀？