请教一道语法题有关GMAT比较级 - ChaseDream

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

答案: E 为什么？
我觉得比较的对象是速度 D中的 That 代替了Speed 为什么错？