Three-year-old Sara and her playmate Michael are both ill and have the same symptoms. Since they play together every afternoon, Sara probably has the same illness as Michael does. Since Michael definitely does not have a streptococcal infection, despite his having some symptoms of one, the illness that Sara has is definitely not a streptococcal infection either. The reasoning in the argument is flawed because the argument ['fails to distinguish between acute streptococcal infections on the one hand, and less severe streptococcal infections on the other', 'presupposes what it sets out to prove', 'mistakes the cause of a particular phenomenon for the effect of that phenomenon', 'treats evidence that the conclusion is probably true as if that evidence establishes the certainty of the conclusion']