In human beings a serotonin-like drug D-Fenfluramine releases

OFFICIAL EXPLANATION


• Split #1: suppresses (wrong) v. suppressing (correct)

Participles (verbING words) such as suppressing that are preceded by a comma often modify the entire previous clause.
Furthermore, ___ING words often present the result of the previous clause.
-- Correct: The sun shone steadily, melting the ice.
-- the word melting, preceded by a comma, modifies the whole previous sentence and presents its result.

The drug D-Fleuramine causes less snacking and less weight gain.

In order to express this result and because their construction precludes suppresses from being a third verb, options A, B, and C should use the participial form, suppressing, rather than the verb form, suppresses.

The verb suppresses could be a third verb, parallel to releases and prolongs, but only if selectively suppresses were preceded by COMMA + AND.
-- At the moment, "...selectively suppresses carbohydrate snacking. . ." is clumsily slapped onto the end of the sentence.
-- Suppresses is a verb that cannot modify the entire preceding clause.
-- suppresses cannot even be the third verb because it is not preceded by a comma + and.

A list of more than two elements (releases, prolongs, and suppresses) requires both a comma and the word "and" before the last element in the list.
That comma is called an Oxford comma.

Oddly enough, given its name, the Oxford comma is not used in British English.
The Oxford comma is not used in American or British journalism in order to save space.

In formal written U.S. English, the Oxford comma is preferred.
And the Oxford comma is always used on the GMAT. I have seen zero exceptions to this rule and I do not expect to see any.

The way that options A, B, and C utilize suppresses is incorrect.

Eliminate options A, B, and C

• Split #2: ITS or THE? Choose the clearer, less troublesome word

Disclaimer: I am not a fan of eliminating options on the basis of pronoun ambiguity.
I leave pronoun ambiguity until the very end of my analysis.
GMAT will tolerate quite a bit of pronoun ambiguity, as I describe in my post about the now-perished "possessive poison" rule, a post that you can find here.

Choose "the" over "its."
The is more logical.
Its has already been used to refer to a different noun.

Option D says, "suppressing carbohydrate snacking, and the weight gain in people who crave carbohydrates."
Option E says, "suppressing carbohydrate snacking, and its weight gain in people who crave carbohydrates."
The carbohydrate snacking does not itself gain wait.
Option E's suggestion is illogical.

At the same time, we are not really confused.
We know from experience with SWE and context that its weight gain refers to the effect of carbohydrate snacking.

But the word its has been used before to refer to serotonin.
We know that its does not refer to serotonin.
Nonetheless, 99% of the time, GMAC does not like one form of a pronoun to refer to different nouns.
That is, correct answers in which two "thems" refer to two different nouns are very rare.

Option E uses its, which both sounds slightly absurd and re-uses a pronoun that has already been used to refer to another noun.

The word "the" in option D poses absolutely no risk.
Choose the no-risk option.

Eliminate option E.

The best answer is D.

NOTES

• Run on sentences? No.

Although I can understand why people might think that options A, B, or C are run on sentences, they are not.

A run on sentence, also called a "comma splice," impermissibly "sticks" two independent clauses together with nothing more than a comma.
Independent clauses contain a subject and verb and can stand alone.
We can join two ICs
(1) with a comma and a coordinating conjunction (FANBOYS: for, and, nor, but, or, yet, so)
(2) with a semicolon—and often, in that case, a word follows the semicolon, such as thereby or thus

The latter two italicized words are called "conjunctive adverbs."
Don't worry about the jargon.
Just know that almost always on the GMAT, conjunctive adverbs follow a semicolon that separates two independent clauses.
-- Correct: The boss was grouchy; consequently, all the employees avoided her.
-- Correct: The boss was grouchy; all the employees avoided her.
-- Wrong: The boss was grouchy, all the employees avoided her.

Options A, B, and C aren't true run on sentences because only one independent clause exists.
We do not have two ICs joined impermissibly by only a comma.
Rather, options A, B, and C contain botched "compound predicates" (one subject is followed by more than one verb).

• Final note
The last [comma + and] is a good example of an instance in which a comma is not technically necessary but is stylistically superior.
You will not be tested on such subtleties!
I highlight the issue only because I see some strange not-rules floating around about comma placement.

COMMENTS

shameekv1989 and bansalsimona ,welcome to SC Butler.
bansalsimona, your question was good, but if I had answered it before the OA posted, I would have given away the OA.

shameekv1989 your analysis is mostly outstanding.

zhanbo and hero_with_1000_faces , good to "see" you again.

This question is slippery and hard.
Kudos to all for being brave.