I would go with (A). This answer choice is definitely not a necessary assumption, as the air-pollution regulations could have caused a 30% decrease in air-pollution and this would cause a lot of changes already.

Ian Stewart wrote: In the original argument, what is the justification for the conclusion? Precisely that there were more birds. It's an unstated assumption that having more birds is a good thing; it's the only justification for improving air quality that is provided. So D is one of the assumptions. A, however, is clearly not assumed in the argument. The argument does not assume that local industry is 'almost entirely' the source of air pollution. It only assumes that regulation on local industry will have a positive effect.

Hi Ian
I have a doubt abt Ans choice D
D says An increase in the number of bird species in and around a city is desirable.
whereas the Stimulus says An increase in the number of bird species seen in and around a city .
The stimuls just talks abt the number of species seen and not species that actually live in the city.The species might be flying over the city from other places in other cities.

Good Q. Initially I also went with E. But read the ans choice again and went for A. Hope I can do this type of re-reading in actual GMAT

Hey Ian , I got a question here. I see no point in how E is assumed. It could be possible that increase in the number of birds in and around the city is due to more birds coming from another city, say manchester, but its not due to increase in the number of species in London.

If B cannot be an assumption, neither can A which is on similar lines..

If the argument is not concerned with improving quality of air (option B) why would Air pollution problems be relevant(Option A)

I go with 'D'. Because negating this argument does not weaken the argument while rest of the options do.

The argument does not establish a causal relationship between regulation and inc. in bird species. It could merely be correlation. Hence, inc. in bird species need not be desirable.

i chose the answer option E but still not able to decipher why the answer is A

IMO A

(D)..The birds may or may not be desirable in city

shipra wrote:2. In the years since the city of London imposed strict air-pollution regulations on local industry, the number of bird species seen in and around London has increased dramatically. Similar air-pollution rules should be imposed in other major cities.
Each of the following is an assumption made in the argument above EXCEPT:
(A) In most major cities, air-pollution problems are caused almost entirely by local industry.
(B) Air-pollution regulations on industry have a significant impact on the quality of the air.
(C) The air-pollution problems of other major cities are basically similar to those once suffered by London.
(D) An increase in the number of bird species in and around a city is desirable.
(E) The increased sightings of bird species in and around London reflect an actual increase in the number of species in the area.

A is assumed, because otherwise it would make no sense for other major cities to impose the same regulations to achieve the same results.
C is assumed, because otherwise what worked for London (imposing air-pollution regulation on local industries) would not work for them.
D is assumed, because otherwise the argument wouldn't even suggest doing something to achieve an increase in the species.

B and E: Air quality isn't mentioned, neither is an actual increase in the number of species. It can be said reasonably that if the regulation-quality link were not being made, the argument would not suggest regulations (similar to A). E remains as the best answer.

I selected (A).. as the word 'MOST' is not going with the passage and exaggerating..

Hi everybody! Can Shipra post the official answer please???

I don't agree that B is the answer,because the quality of air indeed plays a great role on birds' survival and if the regulations do not have significant impact on the polluted air quality then the number of bird's may not increase,so B must be assumed.

As for D,desirability does not affect the logic of the argument,an increase in the number of birds' may or may not be desirable,while regulations will have their intended effect even if the increase is not desirable.So I think the answer is D which does NOT need to be assumed.

I would like to hear experts' opinion on this question if it's possible

OA: D
An increase in the number of bird species in and around a city is desirable. This is NOT RELEVANT when we want to apply a practice which was successful in London to another City. Hence this is NOT AN ASSUMPTION required by the argument.

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shipra wrote:2. In the years since the city of London imposed strict air-pollution regulations on local industry, the number of bird species seen in and around London has increased dramatically. Similar air-pollution rules should be imposed in other major cities.
Each of the following is an assumption made in the argument above EXCEPT:

I received a PM asking me to comment.

The conclusion is that similar air-pollution rules should be imposed in other major cities.
An assumption is something that MUST BE TRUE for this conclusion to be valid.
Apply the NEGATION TEST.

1. Reverse what each answer choice says.
2. Check whether the conclusion remains valid.
3. If the conclusion is invalidated, then the answer choice is an assumption: something that MUST BE TRUE for the conclusion to be valid.

(A) In most major cities, air-pollution problems are NOT caused ALMOST ENTIRELY by local industry.
So what? For the conclusion to be valid, why must it be true that almost ALL air-pollution problems are caused by local industry? If only 75% of the problems are caused by local industry, then regulating local industry would still provide significant benefit.
Since the negation of A does not trash the conclusion, A is NOT an assumption: it does not have to be true for the conclusion to be valid.
Hold onto A.

(B) Air-pollution regulations on industry DO NOT have a significant impact on the quality of the air.
If regulations do not have a significant impact on air quality, then there is little reason to believe that the regulations in London caused the increase in the number of birds, invalidating the conclusion here.
Since the negation of B trashes the conclusion, B is an assumption: something that must be true for the conclusion to be valid.
Eliminate B.

(C) The air-pollution problems of other major cities are DIFFERENT FROM those once suffered by London.
If the problems in other cities are different from those in London, then the conclusion that other cities should impose similar regulations is invalidated.
Since the negation of C trashes the conclusion, C is an assumption: something that must be true for the conclusion to be valid.
Eliminate C.

(D) An increase in the number of bird species in and around a city is NOT desirable.
The argument links the regulations in London to the increase in the number of bird species seen in and around London.
If an increase in the number of birds is not desirable, then why should other cities impose similar regulations?
Since the negation of D trashes the conclusion, D is an assumption: something that must be true for the conclusion to be valid.
Eliminate D.

(E) The increased sightings of bird species in and around London DOES NOT reflect an actual increase in the number of species in the area.
If the number of bird species did not in fact increase, then the link between the regulations and the number of birds is broken, invalidating the conclusion that other cities should impose similar regulations.
Since the negation of E trashes the conclusion, E is an assumption: something that must be true for the conclusion to be valid.
Eliminate E.

The correct answer is A.

Thanks GMATGuruNY! Great explanation!

My home-made analogy:

In a research on cancer patients, a group of lung cancer patients were undergoing a recuperative program that requires daily physical exercises. At the end of the program, the size of the tumor in each of these patients decreased dramatically. Similar recuperative program should be imposed on other cancer patients.

Each of the following is an assumption made in the argument above EXCEPT:

A. In most cancer patients, cancer is caused almost entirely by lack of physical exercises.
B. The recuperative program that requires daily physical exercises has a significant impact on the cancer recuperation.
C. Other cancer patients have disease mechanisms basically similar to those of lung cancer patients.
D. A decrease in the tumor size is desirable for cancer treatment.
E. A decrease in the tumor size in a lung cancer patient reflects improved condition of the patient.