Contrary to what is generally believed the brain being a malleable or

OFFICIAL EXPLANATION



THE PROMPT



• Meaning?
The sentence indicates that the brain is capable of both restructuring and adapting itself within limits.
This capability is known as neuroplasticity.

• Main issue? Modifiers

This question tests The Missing Noun (an idea, a phenomenon).
That is, the main clause describes an event or phenomenon but does not use a noun to do so.
In this instance, the main clause explains that the brain is malleable [adjective] and can do [verbs] two things.

Known as neuroplasticity describes what happens in that main clause.
A something is "known as neuroplasticity"; the latter phrase is an adjective that needs a noun to modify.

We cannot simply "tack on" the noun description known as neuroplasticity because the main clause does not contain the noun we need.

So we create the noun.
We summarize the idea in the main clause.
To do so, we make up a word or a few words to describe the noun-thing that happened in the main clause.
The noun phrase a phenomenon known as neuroplasticity is called a summative (summarizing) modifier.
(Don't worry about the jargon.)

The noun phrase summarizes or encapsulates the idea expressed in the main clause.
Summative modifiers are a special kind of apposition.

THE OPTIONS

• modifier error
→ the inputs are not known as neuroplasticity
→ the the brain is not known as neuroplasticity

• being?
→ in this case, as is often the case, the use of being makes the sentence awkward
→ although the word being is suspect, do not dismiss an "awkward" option on the first pass.
Correct official sentences often seem awkward. Style decisions come last.
We eliminate this option because of the modifier error.
ELIMINATE A


• which must refer to a noun and cannot modify an entire clause.
→ the antecedent of which is either ambiguous or nonexistent
Does which refer to the noun phrase adapting to new sensory inputs?
Or does which refer to the noun phrase restructuring itself?
Alternatively, from context we can surmise that the which clause should refer to the whole idea expressed in the previous clause—but no noun exists for which to modify.

• do not worry about the changed placement of "within limits."
Do not get distracted by this change. This option contains a major modifier error. We can eliminate on that basis alone and not waste time wondering about the placement of "within limits."
ELIMINATE B

• fragment: the main clause lacks a verb
→ this since means because, and we should be dealing with a Because X, Y construction
→ If we ignore the first part of the sentence and simplify, we get this fragment:
Because the brain is a malleable organ, capable and adaptable, a phenomenon known as neuroplasticity.
ELIMINATE C


• I do not see any errors
• a phenomenon properly captures the idea expressed in the previous clause
→ the words a phenomenon create a summative modifier, which I discussed in the introduction.
→ now, known as neuroplasticity correctly modifies a phenomenon (noun)
KEEP

• known as neuroplasticity seems to modify, incorrectly, malleable organ
• the inverted order of the phrases and clauses creates a sentence that is not as effective or clear as that in option D.
ELIMINATE E

The answer is D.

COMMENTS

Jitu20 , welcome to SC Butler.

CEdward , good to "see" you again.

These are trying times that will not last forever.
I am impressed by the consistency of aspirants on GMAT Club.

Keep up the good work.
And stay safe.