Critical Reasoning (CR) | A recent study found that snoring, though not common

A recent study found that snoring, though not common in either group, is more common among smokers than among nonsmokers. On the basis of this evidence, the author hypothesized that smokingby itself can induce snoring.

-- Because of the 'by itself', we need to find an alternate cause. A states an alternate cause. C/D are the same answer, so they are incorrect.

Which one of the following, if true, casts the most doubt on the author’s hypothesis?

(A) Stress induces both snoring and smoking
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