Which of the following most logically completes the argument given?
Asthma, a chronic breathing disorder, is significantly more common today among adult competitive swimmers than it is among competitive athletes who specialize in other sports. Although chlorine is now known to be a lung irritant and swimming pool water is generally chlorinated, it would be rash to assume that frequent exposure to chlorine is the explanation of the high incidence of asthma among these swimmers, since _______ .
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Ayoung people who have asthma are no more likely to become competitive athletes than are young people who do not have asthma
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Bcompetitive athletes who specialize in sports other than swimming are rarely exposed to chlorine
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Ccompetitive athletes as a group have a significantly lower incidence of asthma than do people who do not participate in competitive athletics
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Duntil a few years ago, physicians routinely recommended competitive swimming to children with asthma, in the belief that this form of exercise could alleviate asthma symptoms
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Emany people have asthma without knowing they have it and thus are not diagnosed with
the condition until they begin engaging in very strenuous activities, such as competitive athletics
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