Gmat SC in depth analysis: The Supreme Court

[antest07]

By a vote of 9 to 0, the Supreme Court awarded the Central Intelligence Agency broad discretionary powers enabling it to withhold from the public the identities of its sources of intelligence information.
(A) enabling it to withhold from the public
(B) for it to withhold from the public
(C) for withholding disclosure to the public of
(D) that enable them to withhold from public disclosure
(E) that they can withhold public disclosure of

OA: A

1. OG said that the -ing form modifies "powers". Because -ing form is often wrong in gmat SC, I can't convince myself enabling modifies "powers". Why do we need an -ing form as modifier? What do we call this kind of structure in grammar (e.g. Gerund modifier) ?

2. If I change the sentence as follows:
By a vote of 9 to 0, the Supreme Court awarded the Central Intelligence Agency broad discretionary powers, enabling it to withhold from the public the identities of its sources of intelligence information.
Will the sentence be wrong because "enabling" is now modifying "the Supreme Court"? Again, what do we call this kind of structure in grammar?

[mbadrew]

In this question "enabling" is not modifying powers, rather it's modifying "agency". So, it's in the correct form. One way to check is to take the first clause and cross out the second then see if the first clause will connect with the third clause. What I mean is "By a vote of 9 to 0, cross out this clause, enabling it to ........" Doesn't make any sense does it?

So, the agency is enabled, not the powers of the agency.

Anytime you see the pronoun "it" it should raise a red flag. Check what the it is referring to.

[maihuna]

1. OG said that the -ing form modifies "powers". Because -ing form is often wrong in gmat SC, I can't convince myself enabling modifies "powers". Why do we need an -ing form as modifier? What do we call this kind of structure in grammar (e.g. Gerund modifier) ? Court"? Again, what do we call this kind of structure in grammar?

There are three kind of Verb misuse:
Verb-Noun: Infinitive(to+base verb)
Adjective-Noun: Participle(Verb+ing, +ed/en etc)
Verb-Noun: Gerund(Verb+ing)

Note that though Participle and Gerund look same they are distinguish from the role they play in the sentence. if they modify noun it is participle, if they work as Noun as well as taking objects/adverb etc as the role of Veerb it is Gerund:

Swimming daily is the best exercise: Gerund
Swimming daily, Rakesh built his stamina: participle?Why? Swimming is modifying Rakes han noun here.

Hope it clarifies.