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.
a greater proportion than it was
a greater proportion than
a greater proportion than they have been
which is greater than was so
which is greater than it has been
"a greater proportion" 是 “more than half”的同位语，这个应该没有问题吧。然后把原句改写：Soaring television costs accounted for （more than half）a greater proportion （of） the spending in the presidential campaign of 1992, than soaring television costs accounted/had accounted for a proportion of the spending in any previous election.
再改写：Soaring television costs accounted for （more than half）a greater proportion （of） the spending in the presidential campaign of 1992, than they did/had done in any previous election.
然后复原成同位语形式: Soaring television costs accounted for more than half the spending in the presidential campaign of 1992, a greater proportion than they did/had done in any previous election.
所以A错， 因为1, 如果it用来指代proportion，那么was不对，应该去掉；2，如果it指代TV costs,则明显也不对，应该用they。was不对,应该用were 或者 had been (costs are proportion of ) 或者 应该用did 或者had done （costs accounted for a proportion of），
c错，因为have been事态不对，应该用were 或者 had been (costs are proportion of ) 或者 应该用did 或者had done （costs accounted for a proportion of).b 对，是因为比较前后主谓都一样，可以省略。
http://forum.chasedream.com/GMAT_SC/thread-134429-2-1.html作者: lu80 时间: 2010-8-29 00:34
另：以上同一个帖子中，楼主对时态的分析也很好。作者: hanlei8492 时间: 2010-9-27 21:10
再发问，是否如果答案是“a greater proportion then it”就可以了？作者: z53495532 时间: 2012-12-5 20:57
顶楼主，除了时态 我不太赞同外，其他的地方我跟楼主想的一样。 反正这道题我就这样想的，概括性同位语总结前面整句话，因为其实是两个句子的对比。than后面 Soaring television costs accounted for 和前面相同，因此省略。 因为有介词IN 的补出，所以不会产生与后面时间进行的歧义。 C的话，指代应该是没有问题的，至于时态，我没什么研究，就觉得C的话，没必要用现在完成【现在完成发生的时间在一般过去之后】，貌似就直接用过去式就可以了。作者: Jagabee 时间: 2015-11-4 10:07
Ron不赞同reconstruct the sentence, 而且说a greater proportion than they have been 即便改为a greater proportion than they did 也不对, 因为“did/have done" can't stand for "accounted for"
本人也是错选C, 错误原因有2
1）they必须指soaring tv costs 而不能只是tv costs, then the sentence didn't make sense
2) comparison 平行结构错误. 应为soaring tv costs accounted for more than....soaring tv costs have been ACCOUNTING FOR in any previous election. Ellipsis结构可省略名词但不能省略动词.
