OG SC 18

[ChandraXXX]

1. Computers are becoming faster, more powerful, and more reliable, and so too are modems, they are the devices to allow two or more computers to share information over regular telephone lines.
(A) so too are modems, they are the devices to allow
(B) so too are modems, the devices that allow
(C) so too modems, the devices allowing
(D) also modems, they are the devices that allow

-- The answer is B. But can anyone please explain why C is not correct?

[ajaypatil_am]

so too modems, the devices allowing

GMAT hates '+ing' construct especially in the sentence like this where there is one more clause after 'allow' (to share information over regular telephone lines. )..

[perfectstranger]

1. Computers are becoming faster, more powerful, and more reliable, and so too are modems, they are the devices to allow two or more computers to share information over regular telephone lines.
(A) so too are modems, they are the devices to allow- so too are is correctly used to introduce a second main clause , however the use of ''they are'' is incorrect -
(B) so too are modems, the devices that allow
(C) so too modems, the devices allowing-''Verb ''are'' is needed-
(D) also modems, they are the devices that allow- Use of also is confusing lead us to understand that computers are becoming models ''Computers are becoming faster also modems''
(E) also modems,which are the devices to allow-same as D-

-- The answer is B. But can anyone please explain why C is not correct?