A team of researchers reported that five endangered birds species had

VERBing + OR + VERBing + DIRECT OBJECT
Generally, this structure is appropriate when the direct object is applied to BOTH VERBings.
Mary considered calling or texting her husband.
Here, her husband serves as the direct object for both VERBings.
Conveyed meaning:
Mary considered calling [her husband] or texting her husband.

C: The species had resumed nesting or investigating nesting boxes.
Here, if the direct object in red is applied to the two preceding VERBings in blue, we get:
The species had resumed nesting [nesting boxes] or investigating nesting boxes.
This meaning is nonsensical.
Eliminate C.

Generally:
COMMA + VERBing refers to the nearest preceding action and to the agent of this action.
An official SC in GMATPrep:
Union members are less likely to be enrolled in insurance plans that require doctors to see more patients, spending less time with each.
Here, COMMA + spending refers to TO SEE (the nearest preceding action) and to DOCTORS (the agent of to see).
Conveyed meaning;
Doctors are required TO SEE more patients.
As a result, these doctors are SPENDING less time with each patient.


The verb that you added in bold -- were -- does not actually appear in the sentence.
COMMA + VERBing cannot serve to modify a verb that does not actually appear in the sentence.

Also:
The agent of an action is the entity that PERFORMS the action.
B: boxes erected by volunteers, being
Here, boxes do not perform the act of erecting.
Rather, erected is an adjective DESCRIBING the boxes.
Question: What KIND of boxes?
Answer: boxes ERECTED BY VOLUNTEERS.
Since the boxes do not perform an action, they do not constitute an agent.

I have a doubt on the logical structure of modifiers. Consider Option C (I understand it is an incorrect option due to the reasons explained in the earlier posts):

A team of researchers reported that five endangered bird species had resumed nesting or (c) investigating nesting boxes, erected by volunteers, ferried out to the island last month.

Now, breaking down as follows (please ignore the correct intended meaning for the time being. This is just an example for reference to understand what modifies what in a sentence like this):
1. A team of researchers reported that five endangered bird species had resumed nesting or investigating nesting boxes,
2. erected by volunteers,
3. ferried out to the island last month

My understanding is:
1. "erected by volunteers" (which is framed inside the comma pair) refers to the "boxes".
2. I have a doubt on this one-
(A). Does "ferried" refer to "volunteers"? As per the touch-rule, the verb-ed modifier would modify the closest noun entity in the previous sentence (hence, "volunteers" here).
or, (B). Does "ferried" refer back to "boxes"? As "erected by volunteers" is inside the comma pair and can be considered non-essential (ommitted) for the time-being.

Request to please share your expert inputs here. Thanks in advance.
AndrewN
zhanbo

Hello, Pankaj0901. You should indeed have doubts about (C). The double commas tell us that the modifier erected by volunteers is non-essential, so we should be able to remove that modifier without distorting the meaning of the main clause. But that creates a problem, since the sentence would then be saying that nesting boxes had been ferried out to the island. I suppose the boxes could have been ferried out, but then that leaves the information about the volunteers in an awkward spot. If the sentence means to convey that those volunteers were ferried out to the island, then such information should be restrictive, presented without commas: by volunteers ferried out. Since (C) wedges a comma between volunteers and ferried, we can only interpret the sentence as saying that boxes were ferried out, and, in case we were curious, those same boxes were built by volunteers.

In general, I would urge you not to pursue a line of reasoning that divorces grammar from meaning. The two are often intertwined, as is the case above, and sometimes perfectly grammatical answers still fall flat in terms of the meaning they convey.

- Andrew

MartyTargetTestPrep GMATNinja can you please break down the intended meaning of the sentence for me? it would only make sense that the researches perform the investigation but isnt' the correct answer choice (D) violating parallelism rules?

There's a common misconception that parallelism means that the two parallel elements will look the same or be close to identical. This doesn't need to be the case. It's better to think about it like this: if two elements are parallel, they should play the same grammatical role, and the way they do this should be logical.

Take a simple example:

When Tim gets home from work he needs to take a nap or he will be extremely cranky when it's time to play Pokemon with his kids.

Here, the parallel marker is "or" and the parallel elements are the two clauses in red. Logically, they make sense. Tim can take a nap. Or later he will snap at his kids during their card game.

You wouldn't want to look at those elements and think "Wait. One clause has a present tense verb and the other has a future tense verb, so the parallelism is faulty!" The different tenses work in context, and the two elements are grammatically similar. So it's fine.

Similar situation in (D). Take another look:

The parallel elements in red are both verb phrases, so they play the same grammatical role. It's true that the tenses of the verbs are different, but this difference is logical in context. Imagine that yesterday some kids were looking at birds in a box and that these birds resumed nesting there sometime before the kids saw them. We use the past perfect, "had" to indicate a past action before something else in the past, so it would make sense to indicate the sequence of actions by writing "the birds had resumed nesting," right?

Now imagine that yesterday the kids saw the same birds, but this time the kids observed the birds investigating the box. Well, this time, the action (were investigating) is happening at the same time the kids were observing, so using the past tense "were observing" makes sense.

In other words, the two actions in the parallel construction take place at different times, but that's fine. Both are verb phrases, and the logic checks out -- the birds would resume nesting at some point before they were observed, but they could be investigating as they were observed.

The takeaway: when evaluating parallelism don't look for identical elements! Look for similar grammatical roles that are logical in context.

I hope that helps!

Aahaa... This is much clear. It has caught and corrected the exact psyche/thought process I had.
When a student gets a question wrong, he/she is looking NOT at why a particular answer choice is correct but rather at an explanation that tells how & why the option he/she choose is incorrect.
(A reason that pretty much explains popularity of explanations from experts like GMATNinja, KarishmaB, EMPOWERgmatRichC, mikemcgarry, ScottTargetTestPrep.

This surely is an example of such explanation.

Thanks a lot EducationAisle .

GMATNinja Even after going through all the answers in the forum, I can't understand why C is wrong, I can understand the logic behind D being right - although it makes sense for both volunteers and boxes to be ferried out. So that is a tough decision point.

my underlined reasoning is that if these birds were endangered, they can very resume investigating the boxes, I think that nesting and investigating can be parallel like that. Please correct me where I am wrong.

Sorry that I'm late to the party here!

The problem is that we're talking about nesting boxes that were erected by volunteers LAST MONTH.

If we go with (C), that means that, within one month's time, the endangered birds (1) investigated those nesting boxes, (2) stopped investigating those nesting boxes, and (3) resumed investigating those nesting boxes. That's not impossible, but it seems like an unlikely scenario for a team of researchers to observe and report.

A far more logical scenario is that the team of researchers reported that the birds WERE investigating the nesting boxes that were just put there within the last month -- which is what choice (D) says.

Also, notice that in (C), it's the nesting boxes that were ferried to the island, while in (D) it's the volunteers who were ferried to the island. (C) implies that the nesting boxes were erected by volunteers BEFORE they were ferried out to the island. That's not impossible, but who actually put the nesting boxes in place on the island?

Again, (D) makes more sense: the volunteers were ferried to the island and erected the nesting boxes when they got there. Nice and clear.

Grammatically speaking, "investigating" can certainly be parallel to "nesting" in choice (C), but since choice (D) offers a much more clear and logical meaning, that's our winner.

I hope that helps!

A team of researchers reported that five endangered bird species had resumed nesting or investigated nesting boxes erected by volunteers having been ferried out to the island last month.

Option Elimination -

(A) investigated nesting boxes erected by volunteers having been - "having been" here is a problem. The "having been" - the present perfect participle, is a wired here. Usually, the structure is "Having finished his work, John went for a walk" - the action of finishing work happened before John went for a walk. Present perfect participle is used to indicate an action that occurred before another past action (different from past perfect - in past perfect, the action has been completed in the past before another past action, but in present perfect participle, the effect of that action (that occurred before another past action) is present).

Here, we have action in a sequence - researchers reported - but before that, "resumed" or "investigated" nesting (yes, we can use "had" for both verbs), so "had" is good. Till then, we do not have a problem, but the problem starts with "having been ferried." Did the "having been ferried" happen before birds "nested and investigated" and researchers "reported," or did it happen in between birds "nested and investigated" and researchers "reported"? The sequence is not clear. Here is the correct version of the usage of "having been ferried out to the island last month": "The volunteers, having been ferried out to the island last month, helped erect nesting boxes for the endangered birds." Here, "having been ferried out to the island last month" happened before "helped," and the sequence is precise. But in our question option, the sequence is a mess.

(B) begun investigating nesting boxes erected by volunteers, being - avoid "being" usage as a modifier on GMAT as creates meaning issues. Usage of being as a noun or passive continuous verb.

(C) investigating nesting boxes, erected by volunteers, - had resumed nesting nesting boxes is illogical. Moreover, as "erected by volunteers" is a non-essential modifier, "ferried out to the island last month" can modify "boxes," creating an incorrect meaning. Volunteers and not boxes were ferried out.

(D) were investigating nesting boxes erected by volunteers - This is absolutely fine, as it says when workers reported birds had resumed nesting but were still investigating, indicating that they were actively nesting while also investigating the nesting boxes.

(E) investigate nesting boxes erected by volunteers, which - total mess. "investigate" wrong tense. "which" refers to "volunteers" wrong.