gerund vs particple adjective

[snve]

The data collected by weather airplanes that fly into the heart of a hurricane are useful mainly for gauging the storm’s structure and strength, not for the speed and the path of their movement.
(A) not for the speed and the path of their movement
(B) not for the speed and path of its movement
(C) not the speed and path of its movement
(D) and not the speed and path of their movements
(E) and not for the speed and the path of its movements

hey could Manhattan Staff discuss the difference between b and C

why is parallelism applied as following
for gauging the structure, and not the speed

and not as in B...why has the for been skipped

for X, and not for Y

is their more to it than the ellipsis?

I hope we have a compelling reason to negate B:)

[snve85]

Could anyone from Manhattan Staff help :)

Regards
snv

[rbibhu]

(A) not for the speed and the path of their movement----use of "their" is wrong
(B) not for the speed and path of its movement------not for is wrong
(C) not the speed and path of its movement----Correct
(D) and not the speed and path of their movements---use of "their" is wrong
(E) and not for the speed and the path of its movements-----same reason as in B above.

[ayushrastogi82]

IMO C.

B: useful for gauging X, not for Y - Incorrect, though very tempting but not parallel
C: useful for gauging X, not Y - Correct

[RonPurewal]

if you say "for X, not for Y", then all of X and all of Y must be parallel.

let's break apart choice (b):
not for gauging the storm's structure and strength, but for the speed and path...
this is incorrect. the first part is a gerund, representing an action, and the second is a noun, representing an aspect of the storm.
not parallel.

if you think about the context, it should be very clear that the intended parallelism is between "the storm's structure and strength" and "the speed and path of its movement". these are both nouns, and they're both aspects of the storm.
"gauging" is an action; there are no other actions in the sentence to which it can be parallel.

let's break apart (c):
[i]...are useful mainly for gauging the storm’s structure and strength, not the speed and the path of their movement

that makes sense. there's no second "for" to restrict our choice of parallel structures this time.