Refer this post.
https://www.beatthegmat.com/cant-underst ... 13362.html

Hello,

I don't have it very clear. Can any expert explain to me please!

Thanks

At the risk of being obvious, this is a NOT question. You want the choice that is NOT an assumption.

Now . . .

The conclusion: Similar air-pollution rules should be imposed in other major cities. (The word "should" is usually found in conclusions.)

The evidence: 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.

There are a number of assumptions being made here, four of which are in the choices.

Choice B is an assumption because if air-pollution regulations on industry do not have a significant impact on the quality of the air, then something else was responsible for the bird uptick, and so, NO, one should not impose the rules on other cities.

Choice C is an assumption because if the air-pollution problems of other major cities are NOT basically similar to those once suffered by London, then the plan to impose the rules on other cities is pointless.

Choice D is an assumption because if the increase in bird species is NOT desirable, then why try to export the plan?

Choice E is an assumption because if the increased sightings of bird species in and around London DOES NOT reflect an actual increase in the number of species in the area, the regulations did not cause a change. The plan to try the regulation out elsewhere is pointless.

But Choice A doesn't need to be assumed. This choice uses the word "most" -- "most cities." This does not need to be assumed -- maybe in 50% of cities, air-pollution problems are caused almost entirely by local industry. The plan is still reasonable. Also, do the air problems have to be "almost entirely" caused by local industry? What if local industry was a relatively minor factor in air quality? The regulations might still have been enough to help the birds, and the conclusion still stands. The author of this argument does NOT need to assume what Choice A says.

I'm available if you'd like any follow up.

EconomistGMATTutor wrote:At the risk of being obvious, this is a NOT question. You want the choice that is NOT an assumption.

Now . . .

The conclusion: Similar air-pollution rules should be imposed in other major cities. (The word "should" is usually found in conclusions.)

The evidence: 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.

There are a number of assumptions being made here, four of which are in the choices.

Choice B is an assumption because if air-pollution regulations on industry do not have a significant impact on the quality of the air, then something else was responsible for the bird uptick, and so, NO, one should not impose the rules on other cities.

Choice C is an assumption because if the air-pollution problems of other major cities are NOT basically similar to those once suffered by London, then the plan to impose the rules on other cities is pointless.

Choice D is an assumption because if the increase in bird species is NOT desirable, then why try to export the plan?

Choice E is an assumption because if the increased sightings of bird species in and around London DOES NOT reflect an actual increase in the number of species in the area, the regulations did not cause a change. The plan to try the regulation out elsewhere is pointless.

But Choice A doesn't need to be assumed. This choice uses the word "most" -- "most cities." This does not need to be assumed -- maybe in 50% of cities, air-pollution problems are caused almost entirely by local industry. The plan is still reasonable. Also, do the air problems have to be "almost entirely" caused by local industry? What if local industry was a relatively minor factor in air quality? The regulations might still have been enough to help the birds, and the conclusion still stands. The author of this argument does NOT need to assume what Choice A says.

I truly cannot understand your explanation of choice E being a wrong answer, and choice A being the correct answer.