GWD1-Q16

GWD1-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B。我明白其他四个选项的错误。但是关于B，大家说这个是比较结构的省略形式，因为主从句的主谓是一致的，所以从句部分只保留了介词结构。但是我觉得从句省略部分than后面补全的话应该是than they had in any previous election的啊，因为previous一词暗示从句的动作应该在1992年之前，即过去的过去，那应该是用过去完成时，这样从句过去完成时，主句一般过去时，就不一致了怎么还会因为主谓一致而省略呢？请nn多多指教：）