The traditional treatment of strep infections has been a seven-day course of antibiotics, either penicillin or erythromycin. However, since many patients stop taking those drugs within three days, reinfection is common in cases where those drugs are prescribed. A new antibiotic requires only a three-day course of treatment. Ttherefore, reinfection will probably be less common in cases where the new antibiotic is prescribed than in cases where either penicillin or erythromycin is prescribed. Which of the following, if true, most strengthens the argument? ['Regardless of whether they take a traditional antibiotic or the new one, most patients feel fully recovered after taking the drug for three days.', 'Some of the people who are allergic to penicillin are likely to be allergic to the new antibiotic.', 'Some physicians have already begun to prescribe the new antibiotic instead of penicillin or erythromycin for the treatment of some strep infections.', 'A course of treatment with the new antibiotic costs about the same as a course of treatment with either penicillin or erythromycin.']