58.(27510-!-item-!-188;#058&003569)
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
这里的C选项中的it为什么不能指代level。有人可能说would错，但是我觉得would和will的区别（一个含有推测的虚拟一个不含有）不算是一个考点，那太过于主观了，以一下题为证。所以我想请NN们分析一下than后面常用的it或者those在指代作用上到底有什么规则？谢谢！！
47. Those skeptical of the extent of global warming argue that short-term temperature data are an inadequate means of predicting long-term trends and point out that the scientific community remains divided on whether significant warming will occur and what impact will it have if it does.