Events & Promotions
| Last visit was: 27 Sep 2026, 01:20 |
It is currently 27 Sep 2026, 01:20 |
|
|
GMAT Club Daily Prep
Thank you for using the timer - this advanced tool can estimate your performance and suggest more practice questions. We have subscribed you to Daily Prep Questions via email.
Customized
for You
Track
Your Progress
Practice
Pays
Not interested in getting valuable practice questions and articles delivered to your email? No problem, unsubscribe here.
Sep 2701:30 AM EDT
-02:30 AM EDT
At one point, she believed GMAT wasn’t for her. After scoring 595, self-doubt crept in and she questioned her potential. But instead of quitting, she made the right strategic changes. The result? A remarkable comeback to 695. Check out how Saakshi did it.
Sep 2807:00 PM EDT
-10:00 PM EDT
Boost your GMAT score in less than one month in a live online class + 6 months access to TTP OnDemand video courses included! Class starts Mon, Tues, Wed, Thur, Fri Sept. 28, 2026 - Oct. 16, 2027, 7:00pm-10:00pm EST
Sep 2911:00 AM EDT
-01:00 PM EDT
" Description: Top scores are possible when you enroll in a powerful GMAT course, taught live online + 6 months access to TTP OnDemand video courses included! Class starts Tues/Thur Sept. 29, 2026 - Dec. 3, 2026, 11:00am-1:00pm EST
Oct 0102:00 AM EDT
-03:00 AM EDT
Tejas studied hard but kept repeating the same mistakes. After 3 attempts at 645, a focused 4-week strategy helped him identify and fix what was holding him back—leading to a 695 with just 12–15 hours of study per week.
Oct 0107:00 AM BST
-08:00 AM GMT
Welcome to the GMAT Club's Free Interview Prep Event for Top MBA Programs! Buy tickets - Virtual series that’s all set to equip you to -excel in your MBA interviews.
Oct 0301:00 PM EDT
-04:00 PM EDT
Top scores are possible when you enroll in a powerful GMAT course, taught live online + 6 months access to TTP OnDemand video courses included! Class starts Saturdays Oct. 3, 2026 - Dec. 26, 2026, 1:00pm-4:00pm EST
dgr8sandeep
Joined: 26 Jan 2013
Last visit: 12 Jun 2016
Posts: 20
Given Kudos: 86
Schools: Fisher '17 (II) Smith '18 (A) Jones '18 (WL)
GMAT 1: 680 Q49 V33
Updated on: 15 Oct 2024, 10:58
Originally posted by dgr8sandeep on 03 Sep 2015, 03:45.
Last edited by Bunuel on 15 Oct 2024, 10:58, edited 5 times in total.
Last edited by Bunuel on 15 Oct 2024, 10:58, edited 5 times in total.
Kudos
Bookmarks
C
Be sure to select an answer first to save it in the Error Log before revealing the correct answer (OA)!
Difficulty:
55%
(hard)
Question Stats:
63% (01:53) correct
37%
(02:08)
wrong
based on 10186
sessions
History
Date
Time
Result
Not Attempted Yet
To prevent a newly built dam on the Chiff River from blocking the route of fish migrating to breeding grounds upstream, the dam includes a fish pass, a mechanism designed to allow fish through the dam. Before the construction of the dam and fish pass, several thousand fish a day swam upriver during spawning season. But in the first season after the project's completion, only 300 per day made the journey. Clearly, the fish pass is defective.
Which of the following, if true, most seriously weakens the argument?
(A) Fish that have migrated to the upstream breeding grounds do not return down the Chiff River again.
(B) On other rivers in the region, the construction of dams with fish passes has led to only small decreases in the number of fish migrating upstream.
(C) The construction of the dam stirred up potentially toxic river sediments that were carried downstream.
(D) Populations of migratory fish in the Chiff River have been declining slightly over the last 20 years.
(E) During spawning season, the dam releases sufficient water for migratory fish below the dam to swim upstream.
Which of the following, if true, most seriously weakens the argument?
(A) Fish that have migrated to the upstream breeding grounds do not return down the Chiff River again.
(B) On other rivers in the region, the construction of dams with fish passes has led to only small decreases in the number of fish migrating upstream.
(C) The construction of the dam stirred up potentially toxic river sediments that were carried downstream.
(D) Populations of migratory fish in the Chiff River have been declining slightly over the last 20 years.
(E) During spawning season, the dam releases sufficient water for migratory fish below the dam to swim upstream.
ID: 500276
Solving this question helps.
Taking a timed set of similar questions in
GMAT Club Forum Quiz →
is even better.
02 May 2017, 22:59
Kudos
Bookmarks
dgr8sandeep
Responding to a pm:
Premises:
A fish pass is made on the new dam to allow fish to swim upriver to spawn.
Before the dam, several 1000 fish swam upriver every day.
Now only 300 do per day.
Conclusion: Fish pass is defective.
We have to weaken the argument. So we have to think about why fewer fish may be swimming upstream though the fish pass may not be defective.
(A) Fish that have migrated to the upstream breeding grounds do not return down the Chiff River again.
Irrelevant. What happens to them after the migrate, we don't care. We want to know why they are not migrating.
(B) On other rivers in the region, the construction of dams with fish passes has led to only small decreases in the number of fish migrating upstream.
This strengthens that our fish pass is defective! At other places, the decrease is less. We are seeing a huge decrease.
(C) The construction of the dam stirred up potentially toxic river sediments that were carried downstream.
This provides us a reason why fewer fish are swimming upriver. Perhaps because there are fewer fish now. The construction introduced toxic substances in the river which should have killed many fish. Hence, the fish pass may not be faulty. The problem may be that we have fewer fish now.
Correct.
(D) Populations of migratory fish in the Chiff River have been declining slightly over the last 20 years.
The population has been declining slightly over many years. It doesn't explain the huge decrease in the number of fish swimming upriver.
(E) During spawning season, the dam releases sufficient water far migratory fish below the dam to swim upstream.
The dam is aiding the fish by providing enough water for them to swim upstream. So the fewer fish swimming upstream would not be expected. Hence defective fish pass could actually be the reason.
Answer (C)
20 Aug 2016, 07:55
Kudos
Bookmarks
dgr8sandeep
Conclusion : The fish pass is defective. (X)
Premise : Fishes migrating through the pass has reduced. (Y)
We have X causes Y.
Lets break it. :-D
Option (A) Fish that have migrated to the upstream breeding grounds do not return down the Chiff River again. : Is this a change after the pass or was it happening before also? If before, then it implies it has nothing to do with the conclusion and if after, it implies conclusion is strengthened. Hence , Incorrect.
Option (C) : The construction of the dam stirred up potentially toxic river sediments that were carried downstream. -- Alternate cause for the decrease in number. Hence, weakens the conclusion.
Option (D) : Populations of migratory fish in the Chiff River have been declining slightly over the last 20 years. -- Irrelevant. If it is happening then why did the journey actually reduced after the construction itself. It should have followed the same trend.
Note : We need to find something that explains what happens after construction that made the journey reduction.
Hence, C is the best option with an alternate cause.
General Discussion
dgr8sandeep
Joined: 26 Jan 2013
Last visit: 12 Jun 2016
Posts: 20
Given Kudos: 86
Schools: Fisher '17 (II) Smith '18 (A) Jones '18 (WL)
GMAT 1: 680 Q49 V33
03 Sep 2015, 08:22
Kudos
Bookmarks
Hi drashi,
A weakener just needs to create a doubt in the conclusion. Toxic water may not have killed the fish. But there's a possibility that it could have. In that case, the option weakens the given conclusion.
The author's conclusion is that the fish pass is defective. The basis for this conclusion is that in the first season after the project's completion, only 300 per day made the journey whereas before the construction of the dam and fish pass, several thousand fish a day swam upriver during spawning season.
Possible weakeners for the conclusion:
300 per day doesn't necessarily mean that the fish pass is defective. It could mean:
1) The fish population has gone down.
2) Fish have found a different place other than upstream to go to.
(A) Fish that have migrated to the upstream breeding grounds do not return down the Chiff River again.
-> This is outside the scope of the conclusion. We arent interested in fish that have already migrated upstream.
(B) On other rivers in the region, the construction of dams with fish passes has led to only small decreases in the number of fish migrating upstream.
-> We arent interested in what's happening on other rivers in the region.
(C) The construction of the dam stirred up potentially toxic river sediments that were carried downstream.
-> This is a possible weakener. Toxic river sediments may have brought down the fish population. This is also in accordance with our prethinking.
(D) Populations of migratory fish in the Chiff River have been declining slightly over the last 20 years.
-> This is rather a strengthener. Slight decrease in pouplation doesnt help us to rule out the decrease in population aspect. According to this statement there was no reason why the fish didnt go upstream. Fish pass could thus have been the reason.
(E) During spawning season, the dam releases sufficient water far migratory fish below the dam to swim upstream.
-> This again rules out the possibility that sufficient water wasnt available to go upstream. This is a strenghthner.
Hence, C is the answer.
Hope this helps.
A weakener just needs to create a doubt in the conclusion. Toxic water may not have killed the fish. But there's a possibility that it could have. In that case, the option weakens the given conclusion.
The author's conclusion is that the fish pass is defective. The basis for this conclusion is that in the first season after the project's completion, only 300 per day made the journey whereas before the construction of the dam and fish pass, several thousand fish a day swam upriver during spawning season.
Possible weakeners for the conclusion:
300 per day doesn't necessarily mean that the fish pass is defective. It could mean:
1) The fish population has gone down.
2) Fish have found a different place other than upstream to go to.
(A) Fish that have migrated to the upstream breeding grounds do not return down the Chiff River again.
-> This is outside the scope of the conclusion. We arent interested in fish that have already migrated upstream.
(B) On other rivers in the region, the construction of dams with fish passes has led to only small decreases in the number of fish migrating upstream.
-> We arent interested in what's happening on other rivers in the region.
(C) The construction of the dam stirred up potentially toxic river sediments that were carried downstream.
-> This is a possible weakener. Toxic river sediments may have brought down the fish population. This is also in accordance with our prethinking.
(D) Populations of migratory fish in the Chiff River have been declining slightly over the last 20 years.
-> This is rather a strengthener. Slight decrease in pouplation doesnt help us to rule out the decrease in population aspect. According to this statement there was no reason why the fish didnt go upstream. Fish pass could thus have been the reason.
(E) During spawning season, the dam releases sufficient water far migratory fish below the dam to swim upstream.
-> This again rules out the possibility that sufficient water wasnt available to go upstream. This is a strenghthner.
Hence, C is the answer.
Hope this helps.
