Is "sharing" a verb-ing or a noun?

[FangFang]

Business English Lesson, Advanced Level

ESL/EFL Test #233 "Globalization in Aviation", question 2

One factor affecting civil aviation is the emergence of regional and sub-regional blocs, which provide ......... for sharing of some of the safety responsibility in a common localized geographic approach.

(a) media
(b) modicums
(c) vehicles
(d) viaticums

Business English Lesson, Advanced Level

ESL/EFL Test #233 "Globalization in Aviation", answer 2

One factor affecting civil aviation is the emergence of regional and sub-regional blocs, which provide vehicles for sharing of some of the safety responsibility in a common localized geographic approach.

Correct answer: (c) vehicles
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Hi,

Don't know whether "sharing" is a verb-ing or a noun! If it is a gerund(vt ) ,personally, I think "of " is unnecessary.

Thanks a lot!

[Mister Micawber]

.
It must be a noun, since it is the object of a preposition and has a prepositional phrase as a modifier. You're right, though: the sentence could also be formed without of and converting it to a nonfinite clause head.
.
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Canadian-American native speaker
who teaches English for a living at Mister Micawber's
ESL cafe: Interview with Mr. Micawber