Why do we use destruction, not destroying here?

[ngufo]

The major areas of medicine in which lasers are effective is in the cutting and closing of blood vessels, and in the destruction of tumors.

The correct answer here is "are the cutting and closing of blood vessels, and the destruction" of tumors.

the Princeton guide says: "As you know, some nouns require an "-ing" ending. "Cutting" is one, but the noun form of "destroy" is not " the destroying" its "the desctruction"

But cutting adn closing here are verbs. Why does princeton talk about nouns? Also to be parallel, the answer should be "and the destroying of tumors", shouldnt it?

[mschling52]

This is a tricky one, but I think I do agree with the Princeton explanation on this one.

When you are talking about "the cutting of ..." or the "the closing of ...", cutting and closing are actually nouns. One indicator of this is the use of the article "the", which marks the presence of a noun. Therefore, I think the correct choice would indeed be "the destruction of ... ".

[800GMAT]

Excerpt from American Heritage:

Gerunds are verb forms ending in -ing that act as nouns. They can be the subject of a sentence (Skiing is her favorite sport), the object of a verb (She enjoys skiing), or the object of a preposition (She devoted her free time to skiing). Gerunds can be modified like nouns (That book makes for difficult reading). But they can also act like verbs in that they can take an object (Convincing him was never easy) and be modified by an adverb (Walking daily can improve your health).

[800GMAT]

while I was searching the net for an official defination of a gerund, I came across this grammar site: https://www.bartleby.com/64/1.html