As far back as the 1950s, research has shown that adults who participa

A. The argument talks about prevention of respiratory illnesses. The "some" and the "hereditary" are enough to eliminate this option.
B. Besides the fact that the air pollution is greater, the aerobic exercise could still help to prevent respiratory illnesses. Eliminate B.
C. Since doctors suggest to limit or cease aerobic exercise, maybe aerobic exercise is not enough to prevent respiratory illnesses. But in this option we talk about people who are already affected, so, maybe it is not the right answer.
D. Heart diseases are out of scope. Eliminate D.
E. Less time for aerobic exercise has nothing to do with the argument. Out of Scope. Eliminate E.

Clearly, I can't find any reason to choose an option. Nevertheless, in exam mode I would choose C.

Great discussion on this one. As of today this problem is less than a week old and we've made one change to the official version, changing "incidence" to "prevalence" (so that it's not quite about who CONTRACTS these illnesses but about who HAS them, which therefore makes the problem a whole lot tighter). It now reads:

As far back as the 1950s, research has shown that adults who participate in over 30 minutes of aerobic exercise at least three times a week have a significantly lower prevalence of respiratory illness than those who do not. In recent years, studies have consistently confirmed these same statistics. It can be concluded, therefore, that regular aerobic exercise can be helpful in preventing respiratory illness.

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

A. Some respiratory illnesses are hereditary and therefore minimally affected by lifestyle choices.

B. The amount of air pollution, a common cause of respiratory illness, has increased dramatically since the 1950s.

C. People with respiratory illnesses are generally told by doctors that they must limit or cease their aerobic exercise routines.

D. Recent studies have debunked the conventional wisdom that aerobic exercise is an effective preventer of heart disease.

E. The lengths of the average workday and commute have increased markedly since the 1950s, leaving the average person with less time for aerobic exercise.


With that...(C) is correct, as the real flaw here is one of correlation vs. causation. Is it that people have respiratory illnesses because they don't exercise, or that they don't exercise because they have respiratory illnesses? The conclusion says that exercise prevents illness, but why can't it be that illness prevents exercise?

With choice (A), note that "some respiratory illnesses are hereditary and therefore minimally affected by lifestyle choices" is soft in two spots: if only a couple illnesses are hereditary, the vast majority could still be prevented by exercise, and note that even the hereditary ones can still be affected (albeit minimally) by exercise. The conclusion is also soft, that exercise can be helpful in preventing these illnesses. (A) just isn't inconsistent with the conclusion: it allows for all illnesses to be at least somewhat affected ("can be helpful") and for many illnesses to be very affected (A only rules out some), so (A) leaves the conclusion unscathed.

And (D) just misses the scope of the conclusion, which is only about respiratory illnesses. Since heart disease is a different type of ailment altogether, new information about heart disease isn't necessarily applicable at all to respiratory illness.

Premise - In 1950s, adults who regularly exercise have a lower respiratory illness than those who do not
Premise - In recent years, studies have confirmed these same statistics.
Conclusion - Regular exercise prevents respiratory illness

A. Some respiratory illnesses are hereditary and therefore minimally affected by lifestyle choices. --> minimal affected but doesn't mention that lifestyle will prevent those risks. Out
B. The amount of air pollution, a common cause of respiratory illness, has increased dramatically since the 1950s. ---> We don't know any relationship between air pollution and respiratory illnesses. Out
C. People with respiratory illnesses are generally told by doctors that they must limit or cease their aerobic exercise routines. ---> Exercise can worsen the respiratory illnesses? Not prevent the illness? I will keep this one first.
D. Recent studies have debunked the conventional wisdom that aerobic exercise is an effective preventer of heart disease. ---> Irrelevant we're talking about respiratory illnesses. Exercise might still prevent respiratory illnesses. Out
E. The lengths of the average workday and commute have increased markedly since the 1950s, leaving the average person with less time for aerobic exercise. ---> but the premise shows that recently people still spend about the same amount of time as they did in 1950's. Ok so let think of it mathematically. in 1950's people spent >30 minutes e.g. 60 minutes. How about now prople only spend around 55 minutes? We have no information about the correlation between the length of exercising and the effect on respiratory illnesses. Out

So I got only C. left even I don't really like it but it seem the most relevant to the question.

GMATNinja , broall , mikemcgarry , MartyMurray

How can option C be the OA?? It says that "People with respiratory illnesses are generally told by doctors that they must limit or cease their aerobic exercise routines". As per our conclusion, we are concerned with prevention of respiratory illnesses.

Also many people in the previous posts are inclined towards D. IMO D is incorrect because even though Recent studies have debunked the conventional wisdom that aerobic exercise is an effective preventer of heart disease, aerobic exercises may still be a preventor of respiratory diseases.

Experts please comment

To answer this question, we need a choice that weakens the support for the conclusion. So, one thing that we have to do is to identify exactly what the conclusion is.

Conclusion: Regular aerobic exercise can be helpful in preventing respiratory illness.

We also have to determine how this conclusion is supported. In this case the support for the conclusion is a correlation. The correlation is between exercise and relatively low incidence of respiratory illness. From this correlation, the author concludes that exercise prevents respiratory illness.

However, this correlation could result in multiple ways.

- Exercise prevents respiratory illness.

- Respiratory illness causes people not to exercise.

- People who exercise are less likely to smoke or do other things that cause respiratory illness. So, there is a third factor, healthier living habits, that is associated with both exercise and lower incidence of respiratory illness.

- There could be no clear connection between exercise and lower incidence of respiratory illness. They may just happen to be correlated without there being a known reason for the correlation.

The conclusion is based on the conception that the first - exercise prevents illness - is the reason for the correlation. Information indicating that one of the other relationships is the actual reason would weaken the support for the conclusion.

OK, now let's consider answer choice (D).

D. Recent studies have debunked the conventional wisdom that aerobic exercise is an effective preventer of heart disease.

This choice doesn't give us much useful information. The conclusion is that exercise prevents respiratory illness. The fact that it does not prevent heart disease (a suspect "fact" by the way), does not indicate that it does not prevent respiratory illness. In fact, the argument provides some evidence, the correlation, that exercise does prevent respiratory illness, and this choice does not weaken the support that that evidence provides for the conclusion. I mean, MAYBE we could make the case that, if aerobic exercise does not prevent heart disease, we should question the truth of the idea that it prevents respiratory illness, but really, that case is not very strong.

Now, let's consider choice (C).

C. People with respiratory illnesses are generally told by doctors that they must limit or cease their aerobic exercise routines.

This is interesting, because it provides an alternative explanation for the correlation. This choice gives us reason to believe that, rather than exercise prevents respiratory illness, respiratory illness causes people not to exercise. By providing a clear reason to believe that the reason for the correlation is different from the conception upon which the conclusion of the argument is based, this choice provides a reason to believe that the conclusion may be incorrect.

Thus, choice (C) definitely weakens the argument and is, therefore, a solid OA.

SOLUTION

As far back as the 1950s, research has shown that adults who participate in over 30 minutes of aerobic exercise at least three times a week have a significantly lower prevalence of respiratory illness than those who do not. In recent years, studies have consistently confirmed these same statistics. It can be concluded, therefore, that regular aerobic exercise can be helpful in preventing respiratory illness.

understand :
1)Data - adult who do AE for 3 weeks - lower possibilty of RI than those who dont do AE
Conclusion : Regular AE - prevent RI

Question : WEAKEN

Though process : author concludes that doing X will help in Y . On whatdoes he base his conclusion upon? statistics from past and present. REMEMBER THE AUTHOR DOES NOT PROVIDE US A CAUSAL RELATIONSHIP . He merely stastes the data and then assumes such CAUSE AND EFFECT and then concludes. SO what is author assuming here?
1) there is causal relationship between AE and RI

Framework (what we need?) : an answer choice which will tells us that there actually exists no such relationship and that even when excercising regualrly , there will be no reduction in RI

A. Some respiratory illnesses are hereditary and therefore minimally affected by lifestyle choices.
- conclusion : RAE help prevent RI . the key word in this ans is "some" . This does not gie=ve us enough reason to distrust the author's claim. even if there is 1 person who , if he adobts RAE, can acheive prevention of RI, then the conclusion can still hold true. ALSO , the author say that RAE "CAN" not will help. So the possibility still exists.

B. The amount of air pollution, a common cause of respiratory illness, has increased dramatically since the 1950s.
Irrelevant . Air pollution and it's increament is not related to the conclusion.

C. People with respiratory illnesses are generally told by doctors that they must limit or cease their aerobic exercise routines.
- Reverse logic ( GMAT CR Cause and Effect pattern) . Conclusion : RAE can help prevent RI . But what if YOUR ABILITY TO PERFORM RAE is limited because of RI? If RAE were helpful in prevention of RI , then would doctors recommend them to limit AE? NO... so this breaks the conclusion by implying that there is no cause and effect .

D. Recent studies have debunked the conventional wisdom that aerobic exercise is an effective preventer of heart disease.
- HEART DISEASE ! ... does author specify which disease is he talking about ? NO.. there are a plethora of resp illnesses and HD is one of them . SO even if RAE is ineffective for HD , it could still be effective for other RI's (for example - asthama)

E. The lengths of the average workday and commute have increased markedly since the 1950s, leaving the average person with less time for aerobic exercise.
Irrelevant - The bla bla is limitiamount ofmountof time for RAE does not belittle the claim that RAE CAN HELP PREVENT RI.

Answer C.

I think C is not the answer.
The argument cites that regular aerobic exercise prevents respiratory illness
But in option C it is given that the person is already affected by respiratory illness, then how can we prevent it.

Examine option E, where it is given that in spite of having limited time for performing exercise still people are healthy.

I am not convinced with C as an answer. The option restricts to people with respiratory illnesses.
Let's take an example and work this out. Let's assume there are two persons without respiratory illnesses to begin with, one of whom performs aerobic exercises. Due to the effect of the aerobic exercises, the person contracts respiratory illnesses less frequently than the other person. Would option C work in such a case?

Can experts clarify on this?

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