Neuroscientists, having amassed a wealth of knowledge over the past

Please read my comment again.
The difference is not "now drawing" vs "drawing" (anyway, now is not underlined so it's not optional).

The difference is "now drawing" vs "are now drawing". You are missing the helping verb in (D) which will make it a verb instead of a present participle. Without "are", "drawing" is being used as a modifier (present participle). What you actually need is a proper action verb since this action is taking place.

Neuroscientists have amassed a wealth of knowledge ..., and are now drawing ...
would be acceptable.

Neuroscientists, having amassed a wealth of knowledge..., are now drawing ...
is acceptable (this is option A)

Neuroscientists, having amassed a wealth of knowledge over the past twenty years about the brain and its development from birth to adulthood, are now drawing solid conclusions about how the human brain grows and how babies acquire language.


(A) Neuroscientists, having amassed a wealth of knowledge over the past twenty years about the human brain and its development from birth to adulthood, are-> what is "having". It is modifier. Okay. Neuroscientists are...It's okay too. Let's keep it.

(B) Neuroscientists, having amassed a wealth of knowledge about the brain and its development from birth to adulthood over the past twenty years, and are-> We don't have verb, Neuroscientists....and.

(C) Neuroscientists amassing a wealth of knowledge about the brain and its development from birth to adulthood over the past twenty years, and are-> We don't have verb, Neuroscientists....and.

(D) Neuroscientists have amassed a wealth of knowledge over past twenty years about the brain and its development from birth to adulthood,-> "now drawing solid.... ", here drawing is working a modifier. Which changed the meaning.

(E) Neuroscientists have amassed, over the past twenty years, a wealth of knowledge about the brain and its development from birth to adulthood,->"now drawing solid.... ", here drawing is working a modifier. Which changed the meaning.

So, I think A.

Neuroscientists, having amassed a wealth of knowledge over the past twenty years about the brain and its development from birth to adulthood, are now drawing solid conclusions about how the human brain grows and how babies acquire language.


(A) Neuroscientists, having amassed a wealth of knowledge over the past twenty years about the human brain and its development from birth to adulthood, are CORRECT

(B) Neuroscientists, having amassed a wealth of knowledge about the brain and its development from birth to adulthood over the past twenty years, and are X

The “and” conjunction is unnecessary because it renders the sentence without a main verb.

(C) Neuroscientists amassing a wealth of knowledge about the brain and its development from birth to adulthood over the past twenty years, and are X

Again “and” is unnecessary…we don’t have a main verb.

(D) Neuroscientists have amassed a wealth of knowledge over past twenty years about the brain and its development from birth to adulthood, X

There’s logical connection between the first and second clause of the sentence

(E) Neuroscientists have amassed, over the past twenty years, a wealth of knowledge about the brain and its development from birth to adulthood, X

Same issue as D.

Just a confirmation:

Has Having not similar usage as being - something temporary state or , having been - caused by /existed before particular point of view), an usage that GMAT doesn't prefer usually ?

Shall we keep having not as first priority and choose this option only if other options have definite errors , a strategy that we follow while handling "being"

Experts' Opinion: EducationAisle EMPOWERgmatVerbal AjiteshArun VeritasKarishma please.

Thanks!

AjiteshArun

I have seen some instances where the experts cross off the non-essential modifiers within two commas to make the structure of the sentence less complex. They claim that crossing off the non-essential modifies doesn't take away the meaning of the original sentence.

In this question the Neuroscientists are now drawing solid conclusions about how the human brain grows and how babies acquire language because they amassed a wealth of knowledge over the past twenty years about the human brain and its development from birth to adulthood. So having done X they are now doing Y.

Although removing the modifier. "..., having amassed a wealth of.....," would still not make the right option A grammatically wrong. I wouldn't consider the modifier as a non-essential though because crossing it off would definitely take away the true meaning of the sentence.

Let me know your thoughts.

Hello Vegita,

We hope this finds you well.

To answer your query, the core meaning of this sentence is that neuroscientists are now drawing solid conclusions about how the human brain grows and how babies acquire language; the phrase "having amassed a wealth of knowledge over the past twenty years about the human brain and its development from birth to adulthood" is an adverbial modifier that simply provides more context to an otherwise complete meaning.

We hope this helps.
All the best!
Experts' Global Team

adj/adv clause-ving

Neuroscientists, having amassed a wealth of knowledge over the past twenty years about the brain and its development from birth to adulthood, are now drawing solid conclusions about how the human brain grows and how babies acquire language.


(A) Neuroscientists, having amassed a wealth of knowledge over the past twenty years about the human brain and its development from birth to adulthood, are

(B) Neuroscientists, having amassed a wealth of knowledge about the brain and its development from birth to adulthood over the past twenty years, and are

(C) Neuroscientists amassing a wealth of knowledge about the brain and its development from birth to adulthood over the past twenty years, and are

(D) Neuroscientists have amassed a wealth of knowledge over past twenty years about the brain and its development from birth to adulthood,

(E) Neuroscientists have amassed, over the past twenty years, a wealth of knowledge about the brain and its development from birth to adulthood,

Emily Dickinson’s letters to Susan Huntington Dickinson were written over a period beginning a few years before Susan’s marriage to Emily’s brother and ending shortly before Emily’s death in 1886, outnumbering her letters to anyone else.
(A) Dickinson were written over a period beginning a few years before Susan’s marriage to Emily’s brother and ending shortly before Emily’s death in 1886, outnumbering
(E) Dickinson, which were written over a period beginning a few years before Susan’s marriage to Emily’s brother and ending shortly before Emily’s death in 1886, outnumber

Five hundred million different species of living creatures have appeared on Earth, nearly 99 percent of them vanishing.


(A) Five hundred million different species of living creatures have appeared on Earth, nearly 99 percent of them vanishing.

(B) Nearly 99 percent of five hundred million different species of living creatures that appeared on Earth have vanished.

(C) Vanished are nearly 99 percent of the five hundred million different species of living creatures that appeared on Earth.

(D) Of five hundred million different species of living creatures that have appeared on Earth, nearly 99 percent of them have vanished.

(E) Of the five hundred million different species of living creatures that have appeared on Earth, nearly 99 percent have vanished

MartyTargetTestPrep GMATNinja

Is it right to eliminate (D) and (E) just because the actions "have amassed" can't occur simultaneously with the present-participial phrase "drawing conclusions..."? IMO, it seems to indicate that the neuroscientists were drawing conclusions while amassing a wealth of knowledge. Only after amassing amassing all the information can the conclusion be drawn.

If my reasoning is incorrect, please help me understand why the modifiers in (D) and (E) are incorrect.

You have the right idea here. The "amassing" logically came before the "drawing," and choice (A) expresses that logical meaning in a perfectly clear way.

That said, you could argue that the neuroscientists made some conclusions WHILE they were in the process of amassing the knowledge. In that case, "drawing" could make sense as a modifier for the main clause in (D) and (E): "Neuroscientists have amassed...".

But if that's the interpretation we want, we'd have to drop the "now" to make it clear that the "amassing" and the "drawing" are overlapping actions. The "now" seems to separate the "drawing" and the "amassing" on the timeline, and that throws a wrench in an otherwise plausible interpretation.

Choice (A) avoids this issue by using "drawing" as a verb instead of a modifier: the drawing is happening now, and the amassing happened before that. The meaning is perfectly clear and logical, making (A) a much better choice. (For more on "-ing" verbs vs modifiers, check out this article.)

I hope that helps!