请教GMAT中关于COMPARISON的语法总结

牛奶薏米粥

做PREP08遇见要选比较的就很犹豫，尤其是比较中到底要不要重复代词神马的，就更晕了，想各位好心的CDer求教。比如PREP08中 这道题197. (27650-!-item-!-188;#058&002540)     (GWD-1-Q16)


Soaringtelevision costs accounted for more than half the spending in the presidentialcampaign of 1992, a greater proportion than it was in any previouselection.
A.a greater proportion than it was
B.a greater proportion than
C.a greater proportion than they have been
D.which is greater than was so
E.which is greater than it has been
我选的是A，但是看解释任然不太明白，大概是因为我对比较的对象不清楚，但是究竟要怎么弄清楚还请各位不吝赐教啦
谢谢了，希望各位CDer的考试准备顺利，取得高分~

牛奶薏米粥

谢谢LS，后来自己翻笔记去了，都忘了发的帖子了，谢谢哈

rabbit1937

关键还是看有没有歧义吧

it/they是完全指代，所以变成了指代a greater proportion所以就出现了错误。

C中不至于引起歧义，但是在一些情况下，只有比较前面部分出现同样位置结构的状语之后，后面部分才可以省略为仅有状语。

所以我觉得C对以外，可以写成 a greater proportion than that in any previous election/a greater proportion than the proportion in any previous election