Sentence Correction

lunarpower wrote:
as for the words of the poster above me, i'm actually not sure whether it's possible to stick "now" between the comma and the -ing form in one of these modifiers. i know that it's not flat-out wrong to do this with adverbs in general -- for instance, it's easily possible to insert the word "thus" between the comma and the -ing form -- but, given the rather severe meaning-based restrictions above, i'm just not sure that it's possible to create a sentence in which that meaning would allow for the use of the word "now".
i.e., when you use the word "now", there is usually some sort of transition or difference indicated between the past and the present. in a sentence that is meant to highlight that sort of difference, it's extremely unlikely that you're going to be able to convey an action that is simultaneous with, or is a direct and inevitable result of, the first action -- that would seem to be self-contradictory. therefore, i think it's unlikely that you're going to see "comma + now + VERBing" a as a legitimate modifier.

Ron,

I just want to clarify how this issue (about the use of now between comma and verbing) came up. If you are referring to my post above, I never made this point. The sentences in color are exactly choices D and E.

Thanks.

Right. I understand what you are saying.

I still have a question, though it is not relevant to GMAT -

Let us say we do not have now there -
Neuroscientists have amassed a wealth of knowledge, drawing solid conclusions about how the human brain grows.

Here comma + ing modifier is incorrectly used. Is this a grammatical error or just an error which leads to incorrect meaning?

Generalizing this, are errors due to incorrect use of modifiers under the domain of grammatical errors?

P.S. - I know that I am unnecessarily fretting on useless nomenclatures and classifications. Still, this clarification would help.

Hello Everyone!

Let's tackle this question, one issue at a time, to find the correct answer quickly! First, here is the original question, with the major differences between the options highlighted in orange:

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,

After a quick glance over the options, there are clearly a few things we can focus on:

1. Where to place the phrase "over the past twenty years"
2. How each option begins (modifiers, non-essential phrases, verbs)

Let's start with #1 on our list: where to place the phrase "over the past twenty years." This phrase is meant to modify, or add more detail, to some part of this sentence, but which part? WHAT was done over the past 20 years? Let's take a closer look at each option, and figure out the best location for that phrase:

(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 --> OKAY
It's clear that what happened over the past 20 years was researchers amassing a wealth of knowledge, so let's keep this one for later.

(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 --> WRONG
This is misleading because it suggests that the phrase "over the past 20 years" is modifying "development from birth to adulthood." The research isn't over the past 20 years of someone's life - the research was collected over the past 20 years.

(C) Neuroscientists amassing a wealth of knowledge about the brain and its development from birth to adulthood over the past twenty years, and are --> WRONG
Again, this is misleading because it suggests that the research covers the brain development over 20 years of a person's life, which isn't the intended meaning. It's supposed to say that the research was collected over the span of 20 years.

(D) Neuroscientists have amassed a wealth of knowledge over past twenty years about the brain and its development from birth to adulthood, --> OKAY
It's clear that the research was collected over a span of 20 years, so let's keep this one for later.

(E) Neuroscientists have amassed, over the past twenty years, a wealth of knowledge about the brain and its development from birth to adulthood, --> WRONG
While this isn't grammatically incorrect, it does change the meaning of the original sentence slightly. By putting the phrase "over the past twenty years" in between commas, it's now a non-essential clause. By making this an "optional" phrase, we are saying that the length of time it took to amass this information isn't important. We would argue that it is important because it adds more detail to the idea that it took 20 years to gather all the information, and that neuroscientists are ONLY NOW figuring out what to do with all the information.

We can eliminate options B, C, and E because they place the phrase "over the past twenty years" in the wrong place.

Now that we're only left with 2 options, let's take a closer look at each one to determine which is the best choice. To make this easier, I've included the remaining part of the sentence at the end:

(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 now drawing solid conclusions about how the human brain grows and how babies acquire language.

This is CORRECT! The phrase "over the past twenty years" is in the best location to create clarity and provide accurate information. The non-essential modifier, "...having amassed...to adulthood" uses the right punctuation and doesn't create any problems with verb tenses.

(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 conclusions about how the human brain grows and how babies acquire language.

This is INCORRECT for a couple reasons. First, it uses the present perfect "have amassed," which means that neuroscientists started looking for knowledge in the past and are still looking for it today. This isn't true. They collected all the information in the past, and they are done looking for it - they've moved on to drawing conclusions about brain development based on what they already found! Second, the modifier "now drawing solid conclusions..." sounds like it's in the wrong place, or needs to be worded more clearly to show that it's talking about the neuroscientists drawing conclusions. It's not technically wrong, but it could be confusing to readers.


There you have it - option A was the best choice after all!


Don't study for the GMAT. Train for it.

when we use to do/doing in writing a sentence, give them tense and agent, who perform to do/doing. to do/doing can refer to no specific noun/agent in the sentence to a general persons.
when we read to do/doing , give them tense and agents. this process is the skill to solve sc with to do/doing