求教一道GWD语法！！！！

. GWD21-Q1:

According to analysts, an alliance between three major personal computer companies and most of the nation’s largest local telephone companies would enable customers to receive internet data over regular telephone lines with speeds much higher than is currently possible.

A.     with speeds much higher than is

B.      with speeds that are much higher than are

C.     at much higher speeds as are

D.     at much higher speeds than that

E.      at speeds much higher than are

这题为什么答案是E呢？前面没有出现BE动词 为什么比较要补出BE动词呢？

这里后半句省了主语，speeds。。应该补足就是alliance would enable ..at speeds higher than (speeds) are currently possbile.

因为主语相同，就省略了。。只留下谓语和表语。。

  我的意思是 前面那个speed前面没有Be动词修饰 为什么than后面就可以补出Be动词呢？