Around 1900, fishermen in the Chesapeake Bay area landed more than

GMATNinja
Thanks for the nice explanation. +1.
Could you discuss the meaning of the following 3 versions, please? Always expecting wonderful explanation from you

"The dog, having eaten Dana's homework, is no longer hungry."

"The dog having eaten Dana's homework is no longer hungry."

"The dog, which has eaten Dana's homework, is no longer hungry."

--
Also, it is better to explain the usage of 'shad' in choices A and E. Is 'shad' an adjective in A and E?
Thanks__

GMATNinja,
Hello Sir,
I'm going to tag you again thinking that you missed my query!

Dear GMATGuruNY,

Why can't we use the same reason you posted below to reject choice B. in this question?


According to choice B. in this question, "blocked" were after "had reduced", conveying illogical meaning.

Also choice A. indicates that "overfishing and the proliferation of milldams and culverts" still exists in present. Since choice A. has logical meaning, choice B. certainly distorts the intended meaning.

Could you please clarify?

The simple past tense can serve to express a PAST GENERAL TRUTH: something that was true not at a specific moment but was true in general.
Mary found a dirt road that connected the town to the city.
Common sense tells us that the modifier in blue does not refer to a specific moment but to the GENERAL NATURE of the dirt road.
As a general truth, the dirt road CONNECTED the town to the city.

OA: By 1920, milldams that blocked shad from migrating up their spawning streams had reduced landings.
Here, the modifier in green does not refer to a specific moment but to the general nature of the milldams.
Question: What KIND of milldams?
Answer: Milldams THAT BLOCKED SHAD FROM MIGRATING.
The past action here -- blocked -- does not refer to a specific moment but expresses a GENERAL TRUTH about the milldams.
The sentence conveys that -- by 1920 -- this type of milldam HAD REDUCED landings.
The purpose of the past perfect (had reduced) is to convey that the act of reducing was completed before the modifier in blue.

In contrast:
there was/were serves to express something that was true NOT in general but only AT A SPECIFIC MOMENT in the past.
There were ten women in the room.
Conveyed meaning:
As a SPECIFIC MOMENT in the past, ten women were in the room.

Illogical: Scientists had discovered that there were 17 nearby stars.
Here, the portion in red refers to a SPECIFIC MOMENT in the past that happened AFTER the past perfect action in blue.
This sequence is illogical, implying a discovery EARLIER IN THE PAST (had discovered) about a moment that happened LATER IN THE PAST (there were stars).

Thank you for beautiful response sir GMATGuruNY

I'm not quite clear why is present perfect tense in choice A. wrong?

Why is it illogical to say that blocking started in the past and remains in effect today?
"Milldams and culverts" are long-lasting infrastructure. So, IMO, it makes sense to say that the blocking is still relevant til now.

The present perfect serves to express a PAST ACTiON THAT AFFECTS THE PRESENT.
If there is no time modifier, the implication is that the action was performed in the RECENT PAST.
Biologists at the local university have discovered a bacterium that can withstand extreme heat.
Here, the present perfect verb in blue serves to express a RECENT discovery that affects our PRESENT knowledge of bacteria.

A: Around 1900, fishermen in the Chesapeake Bay area landed more than seventeen million pounds of shad in a single year, but by 1920, over-fishing and the proliferation of milldams and culverts that have blocked shad migrations up their spawning streams had reduced landings to less than four million pounds.
Here, the intention is to express actions that affected times in the PAST (1900 and 1920).
Thus, there is no justification for the use of present perfect verb in red, which implies an action performed in the RECENT PAST.
A good rule of thumb:
STAY IN ONE TENSE unless a change in tense is required.
Here, the main verbs (landed and had reduced) are past tense verbs.
Since the sentence does not require a change in tense, the verb in red should also be in the past tense.

GMATNinja egmat VeritasPrepBrian I was able to eliminate all but options B and E. Could you please explain why Option E can be eliminated.

Hi doeadeer,

Although there are other issues in E, a quick way to take E out is to focus on the their.

The correct option uses the word "shad". Option E, however, uses "shad migrations", in which the main word is migrations. This is not particularly good for the their after up, as the their now seems to point to migrations.

GMATNinja GMATNinjaTwo egmat EducationAisle sayantanc2k

Please could I now what does "their" in "their spawning streams" refer to?

The word spawning is generally used to refer to the reproduction of fish, thus "their spawning streams" I guess is used to modify "Shad". But isn't Shad singular"


Usage of "having" in (D) and (E)
E.g Having done his homework, Ron went out to play.

In the above, the "having done his homework" denotes an action that is already taken place and post this action, Ron went out to play.

Keeping the above in mind I wasn't able to understand why "having blocked" in (D) and (E) is incorrect?

As discussed above, it makes more sense to use "having" with incidental information set off by commas. So the second example is something that you probably wouldn't ever see.

The third example sets off the "which..." part with commas, implying that there is only one dog and that the "which..." part isn't crucial information. (By the way, you probably want to use "who" instead of "which" if you want to avoid the wrath of dog lovers who like to think that their pets are really people!).

But, as with most things SC, the goal here is NOT to come up with a list of black and white rules that can be blindly applied to other problems (i.e. "'having' set off by commas means X, a noun modifier set off by commas means Y, a noun modifier NOT set off by commas means Z...). The explanation above is meant to show how the choice of "that" vs "having" subtly affects the meaning in this particular example. Is that difference a rock solid reason to eliminate D? Nope. But it's a vote in favor of B over D.

As for (A) and (E): "shad" certainly modifies "migration." But that doesn't quite mean that it's an adjective. It's absolutely fine for nouns to modify other nouns (i.e. "blueberry muffin" or "town hall"). These are called attributive nouns, if you like the jargon.

I hope that helps a bit!

The word "shad" (like the word "fish") can be either singular or plural. So "their" does in fact refer to "shad."

As for your question about "having": have you tried reviewing this post?

Hi GMATNinja VeritasKarishma egmat

why not 'had blocked' as in the below sentence?
by 1920 over-fishing and the proliferation of milldams and culverts that had blocked shad migrations up their spawning streams reduced landings to less than four million pounds.

is 'that blocked' in choice B actins as Noun + Noun modifier or as a verb?

VeritasKarishma GMATNinja ChiranjeevSingh
Do we need conjunction to seperate both action blocked and had reduced?

If not then why

Posted from my mobile device

Isn't there is meaning change in correct question tense error blocked happen after dams had reduced landings

The two actions are not connected.

"that blocked shad from migrating ..." is a "that clause" modifying milldams and culverts

So the second independent clause is:
"... over-fishing and the proliferation of milldams and culverts (modifier) had reduced landings ..."

Is the word 'that' referring here to the action "over-fishing and proliferation" ?? Or 'that' is referring to the noun phrase "over-fishing and proliferation of XX "

Due to this decision point I eliminated the first 3 options. Is there any way to tell when the usage of 'that' (in such convoluted cases) is correct?

None.

that refers to the proliferation of milldams and culverts, because from a logical (intended) meaning perspective, proliferation of milldams and culverts blocked shad from migrating up their spawning streams.

p.s. Our book EducationAisle Sentence Correction Nirvana discusses modifier issues of "that", their application and examples in significant detail. If you or someone is interested, PM me your email-id; I can mail the corresponding section.

Interesting question! First, I'd take anything you read in an official explanation with a grain of salt. The explanations aren't written by the same folks who write the questions, and so while some explanations are good, others are a little suspect.

Here's how I think they're reasoning: there's a difference between a concrete action completed at a specific time in the past, and a more abstract action that occurs over a prolonged period of time. Consider two examples:

1) By late 2019, the Tampa Bay Raptors had won a single NBA championship.

In this case, the team won their title at a specific time (June 2019) and this completed action occurred before another past tense marker (late 2019.) Therefore, it makes sense to use the past perfect ("had won") here.

Compare that with the following:

2) The Tampa Bay Raptors did not win a title until 2019.

This sentence is more like the second option in the official question. Now the action -- not winning a title -- doesn't occur at a specific time. It's not like you can point to May 13, and say "that's the day they failed to win the title!" Failing to do something is more abstract. So in this case, because we don't have a concrete action completed at a specific time before another past tense marker, it's fine to use the simple past, "did."

That said, am I 100% confident that it's definitively wrong to write "The Tampa Bay Raptors had not won a title until 2019?" No. I'm not. And I think it's misleading to make it sound as though it's an obvious grammatical error. After all, 2019 was the past, and the team wasn't winning the title before that year, so it's not like this reasoning is totally outlandish. It just doesn't feel as ironclad as the first sentence when you certainly needed to use "had."

And for what it's worth, if I encountered the second construction on the exam, I'd look for a clearer error before eliminating an answer choice. As you noted, the "it" in the second official example seems to be standing in for "a sighting," a noun that doesn't show up elsewhere in the sentence. This is a much better reason to get rid of that option than the supposedly faulty usage of the past perfect.

I hope that helps!

Hello GMATNinja,
I was wondering whether you could help me with this one , I get why B is the correct one , I just want to make sure that I have understood why D is incorrect, in our case having is without commas so having blocked refers back to proliferation (of milldams and culverts modifies proliferation) and that doesn't make sense because proliferation did not block the shads, (some specific milldams and culverts did-that's why we want a "that") on the other hand if we had commas then it would be a non-restrictive modifier and having would not have an impact on the sentence-it could even be removed, so it would be considered correct.