Unlike any other bird, the hummingbird has ball-and-socket shoulder jo

Question

Unlike any other bird, the hummingbird has ball-and-socket shoulder joints that allow it to rotate its wings 180 degrees in all directions. Hummingbirds also have the unique ability to perform several feats of acrobatic flight, such as flying backward, flying upside-down, and hovering.

If the above statements are true, they provide the most support for which of the following claims?

A. Some birds cannot hover. 
 B. It is not possible for a bird without ball-and-socket shoulder joints to fly backward or upside-down. 
 C. Birds without ball-and-socket shoulder joints develop alternative modes of acrobatic flight.
 D. Birds that cannot perform acrobatic feats have no need to rotate their wings 180 degrees in all directions. 
 E. When other birds engage in acrobatic flight, their wings rotate less than 180 degrees.

Unlike any other bird - assumption - hummingbird is the only one with the activities 
So A) is obviously wrong choice - The correct inference would have been "no other" bird can hover - isn't it? It is only HB which can..
B) HB "also" have ability implies that the first sentence is connected to the second - also assumes link between ball and socket with unique ability - inference thus - what is stated
The others are off topic

Chethan92 · Answer

DebbieChats , Can you remove the off topic and other doubts you have from the answer options and ask in the spoiler?

ajmekal · Answer

A detailed explanation, please?
IMO B is correct as "unlike other birds" is used and secondly "unique abilities" is mentioned, both of which signify that only hummingbirds perform can these activities. 
Option A refutes the argument by using "some". "None of the other" would have been an equally valid choice?

Please share your thoughts.

gmexamtaker1 · Answer

Hi, 
Could an expert provide his opinion about this one... I chose B, because I focused on the phrases"unlike any other bird and" and "unique ability to perform..." so I I thought A is wrong, because by some we assume that there is a number of birds that can actually do those things, thus eventually contradicts with the stem right?

sayan640 · Answer

Humming birds have the unique ability to perform "hovering". That definitely means there are some birds who can not hover.
Option A follows and is the answer.
 VeritasKarishma  / 
 GMATNinja  right ?

Posted from my mobile device

MartyTargetTestPrep · Answer

Great question ajmekal, and here's the thing to be aware of regarding the use of the word "some."

"Some" can represent any plural number.

If it is true that very few people like swimming, then "some people" like swimming.

If it is true that most people like swimming, then "some people" like swimming.

If it is true that all people like swimming, then still, "some people" like swimming.

At the same time, people don't necessarily think of "some" as representing "all" or "most." "Some" has multiple connotations, and can be perceived as representing a relatively small fractional proportion of a total.

Because "some" has these connotations, it is used in GMAT Critical Reasoning questions to obscure the meanings of choices, and to make incorrect answers seem correct and correct answers seem incorrect.

In this case, the idea is that all birds other than the hummingbird cannot hover. Clearly, if all birds other than the hummingbird cannot hover, then it is true that some birds cannot hover.

So, if you agree that the passage indicates that only hummingbirds can hover, which inference is actually somewhat debatable, then (A) is correct.

(Whether choice (A) is actually correct is debatable, as the passage could be interpreted as saying that only the hummingbird can perform all of the "several feats of acrobatic flight," leaving open the possibility that other birds can perform one or more of those feats, just not all of these feats.)

KarishmaB · Answer

Yes, you are right. It certainly seems that this is what the test maker wanted you to infer. But I certainly feel an ambiguity in the way it is written.

Is the ability to perform several feats unique (other birds can perform one or two of them but not several)? Or is the ability to perform each of those feats unique (no other bird can hover, no other bird can fly backwards etc)? 
Though if all birds could hover, one would not be able to say that it is a "feat of acrobatic flight". It would be just a part of flying.

chaitnya10 · Answer

I have problem with the answer. If it were an inference question, A would have been right. But for a strengthen question, I think B is better.

URv · Answer

my take:

Option B is incorrect because information presented does not relate the ball and socket joint to the several feats of acrobatic flight, though it might look like it is an obvious conclusion these 2 statements are separate and shouldn't be related as one implying another.

Hence the right option is A.

Unlike any other bird, the hummingbird has ball-and-socket shoulder jo

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Unlike any other bird, the hummingbird has ball-and-socket shoulder jo

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