新prep2-197

197.
                (27650-!-item-!-188;#058&002540)     (GWD-1-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.

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

答案是B，A为什么不对，是因为省略吗？D和E是因为which不能只带整个句子吗？请帮忙解释一下，谢谢。

说的太好啦！！！谢谢 一下子就明白了 而且能够举一反三！