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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.

1. with speeds much higher than is

2. with speeds that are much higher than are

3. at much higher speeds as are

4. at much higher speeds than that (are)

5. at speeds much higher than （speeds ）are  

a: E  我分不清D和E那个更好 

1.are 没有对称的动词 that 好像不完整 

2. at a speed of 是不是固定用法？好像两种都有

3.data 用复数还是单数  

4.括号里的省略对吗？

还是that 换乘those 就对了？

E is the best

1.  than and as  can replace subjects in clauses (rather like relative pronouns).

The train might be late, as happened yeterday.  (NOT....as it happened yesterday.)

As is well known, smoking is dangerous.  (NOT As it is well known.....)

2.  at a speed of   is a phrase.

3.  data 用复数  其单数是 datum.  

Data is a synonym for facts and statistics and is always plural, although it is increasingly used as a singular noun.  

The data show that few drivers observe posted speed limits any more.  

A single fact is a datum, but the word is rarely used.  Rather, "a piece of data" would do just fine.

Cannot agree more!