Learning how to build a nest plays an important part in the breeding

Question

Learning how to build a nest plays an important part in the breeding success of birds. For example, Dr. Snow has recorded the success of a number of blackbirds in several successive years. He finds that birds nesting for the first time are less successful in breeding than are older birds, and also less successful than they themselves are a year later. This cannot be a mere matter of size and strength, since blackbirds, like the great majority of birds, are fully grown when they leave the nest. It is difficult to avoid the conclusion that they benefit by their nesting experience.

Which one of the following, if true, would most weaken the argument?

(A) Blackbirds build better nests than other birds.

(B) The capacity of blackbirds to lay viable eggs increases with each successive trial during the first few years of reproduction.

(C) The breeding success of birds nesting for the second time is greater than that of birds nesting for the first time.

(D) Smaller and weaker blackbirds breed just as successfully as bigger and stronger blackbirds.

(E) Up to 25 percent of all birds are killed by predators before they start to nest

BarneyStinson · Accepted Answer

Guys, those of you who got this wrong must seriously read PowerScore CR bible. Don't waste time and catch hold of that book immediately. There are specific rules you must follow to get to the answer.

Rule 1: Always identify the conclusion and premises. If you are not able to do that, rephrase the sentences in your words in your thoughts to make a cause and effect statement. The effect is your conclusion and the causes are the premises. 
Rule 2: Strengthen, Weaken and Assumption questions more often than not impact the conclusion. 
Rule 3: Particularly you must inculcate the ability of identifying the wrong answer options and the tricks used for them. Option C is a classic Shell game answer and Option D is a classic out-of-scope answer option.

If the conclusion, the first sentence of the given stimulus, claims that building better nests is the reason to successful breeding, to weaken it, all you have to do is look at the answer option that refutes it. How about improved fertility and vigor and not just better nests for successful breeding, is what that weakens the conclusion. Pretty straight forward, a weakening answer option attacks the conclusion that this is not all what it is, it could as well be something else.

11MBA · Answer

The answer should be B.

The statement concludes that blackbirds benefit from their nesting experience, because they breed more successfully with each trial. However, if the capacity of blackbirds to lay viable eggs increases with age then it's not the experience that's affecting success of breeding. Instead it's an inherant biological factor that has nothing to do with experience.

Bunuel · Answer

Official Explanation

Remember, to weaken an argument, typically you must show that a suppressed premise is false. The premise of the argument is that all other things being equal the breeding success of blackbirds increases with experience. To weaken the argument, we need to show that not all things are equal. Choice (B) does this, suggesting that as blackbirds mature they lay more viable eggs. This alone could explain the breeding success of older blackbirds.  The answer is (B).

vibhaj · Answer

B
When it asks for ^weaken^,we should ask "why the nesting exp only?" why not anything else but nesting ? this way we will attack the author's position that nesting exp only was the factor in success.
using this methodology, i was expecting some ans choice that talk abt anything but nesting n here is B that exactly does that.
examined once more and dismissed rest as incorrect

Posted from my mobile device

semwal · Answer

Learning how to build a nest plays an important part in the breeding success of birds.  For example, Dr. Snow has recorded the success of a number of blackbirds in several successive years. He finds that birds nesting for the first time are less successful in breeding than are older birds, and also less successful than they themselves are a year later. This cannot be a mere matter of size and strength, since blackbirds, like the great majority of birds, are fully grown when they leave the nest. It is difficult to avoid the conclusion that they benefit by their nesting experience.

Which one of the following, if true, would most weaken the argument?
(A) Blackbirds build better nests than other birds. IRRELEVANT 
(B) The capacity of blackbirds to lay viable eggs increases with each successive trial during the first few years of reproduction. INSTEAD OF NESTING EXPERIENCE , THIS COULD BE THE REASON FOR BETTER BREEDING LATER...CORRECT 
(C) The breeding success of birds nesting for the second time is greater than that of birds nesting for the first time. ITS ALREADY GIVEN IN STIMULUS .....IT IS JUST A PREMISE... 
(D) Smaller and weaker blackbirds breed just as successfully as bigger and stronger blackbirds. THIS STRENGTHENS THE ARGUMENT..NOTE  "This cannot be a mere matter of size and strength, since blackbirds, like t........ . 
(E) Up to 25 percent of all birds are killed by predators before they start to nest IRRELEVANT

KUDOS IF U PLEASE.....

Skywalker18 · Answer

The key to (B) is understanding the term "capacity." In this context, it means ability - kind of like in a physiological context. In other words, (B) says that it is NOT the nesting experience that leads to more success in breeding but RATHER it is the adaptation of their bodies - every time they lay eggs, they get better!

-Year 2 of breeding was more successful than Year 1; Year 3 was more successful than Year 2
-This cannot be explained by size and strength
-It must be explained by their nesting experience

I simply want to show why it is NOT the nesting experience that led to this. Maybe the blackbirds get progressively healthier during their first years of nesting. Either way, I just want to show an alternative explanation as that is basically the best way to weaken this claim.

(A) "Other birds?" Who cares?

(B) Yea! If the ability to lay more viable eggs increases, then it is NOT the nesting experience but rather their physiology that explains the uptick in success: their eggs are more viable!

(C) We basically already knew this: premise booster.

(D) This actually strengthens by ruling out an alternative explanation. It says that strengthen and size don't matter! Thus, we couldn't just say, "well during the 2nd and 3rd years the birds were stronger or bigger!" to weaken this claim because (D) says, "not so fast! Those things don't matter!" Whenever we rule out an alternative explanation, we are strengthening the argument if just by a little.

(E) "All birds" is too wide of a scope and we don't care about happens before they start to nest - we care about what happens after!

chrtpmdr · Answer

The very first sentence marks the conclusion? 
I was equally confused as some others with the structure of the argument.

Somehow totally narrowed in on the "nest-building" part while negleting the breeding part.

Tough!

VerbalBot · Answer

Automated notice from GMAT Club VerbalBot: 

A member just gave Kudos to this thread, showing it’s still useful. I’ve bumped it to the top so more people can benefit. Feel free to add your own questions or solutions.

 This post was generated automatically.

Learning how to build a nest plays an important part in the breeding

Prep Toolkit

Top 5 GMAT Debrief Videos

615 to 715 in 15 Days (Ria's Strategies)

More than Quant/Verbal Abilities: Speed vs. Accuracy

745 with Only Self-Prep and GMAT Club

From 555 to 765: 210-point Improvement

Perfect 805 Score Debrief by Julia

My Rewards

GMAT Critical Reasoning (CR) Questions

Learning how to build a nest plays an important part in the breeding

Prep Toolkit

615 to 715 in 15 Days (Ria's Strategies)

More than Quant/Verbal Abilities: Speed vs. Accuracy

745 with Only Self-Prep and GMAT Club

From 555 to 765: 210-point Improvement

Perfect 805 Score Debrief by Julia

My Rewards