GWD一题，就是搞不懂？

Q16:

Soaring television costs accounted for more than half the spending in the presidential campaign of 1992, a greater proportion than it was in any previous election.

1. a greater proportion than it was
2. a greater proportion than
3. a greater proportion than they have been
4. which is greater than was so
5. which is greater than it has been

为什么该选B,选A又错在哪里了，谁能告诉我啊！

B,C争议题 A错的原因是it没有指代对象

B补全是a greater proportion than costs accounted (for?) in any previous election。

首先A中的it不能指代前面的 Soaring television costs.要用they

其次就算可以指代也错， 因为 比的是以前竞选时候的成本，如果用了代词则会出现自己和自己比！这也是不对的！

1. 有过总结 it必须带着修饰词比较：因为it是精确的指代前文提到过的事物。比如用it就表示 a greater proportion than a greater proportion

2  这里 gmat比较喜欢的表达应该是 a great proportion than that in previous years 注意没有 动词。加了动词就是比较结构前后不平行。

可为什么还是读着觉得B比较别扭呢，我当时选了C. 现在想想其实关键就是要弄清楚到底比较对象是谁。比较对象是1992的proportion和1992之前的proportion而不是其他，不是costs.所以C是错的。按照they的知道只能是指代的前面的costs况且，就算是they代表的是proportions也有问题，因为后面是in ANY previous evlection 单复数不吻合。

对于A选项为什么it 指代不清，提供一点小看法
            

原句:
        Soaring … campaign of 1992, (假设
        which is 省略) a greater proportion than it was in any previous election.

代名词优先代替原体主词，所以it 应该指代关系代名词which，

而which 又是指1992，必错