问一道题,大家帮忙

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.  Therefore, 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?

1. Some of the people who are allergic to penicillin are likely to be allergic to the new antibiotic.
2. A course of treatment with the new antibiotic costs about the same as a course of treatment with either penicillin or erythromycin.
3. The new antibiotic has been shown to be effective in eradicating bacterial infections other than strep.
4. Some physicians have already begun to prescribe the new antibiotic instead of penicillin or erythromycin for the treatment of some strep infections.

这个前两天有讨论帖，楼主找看看

答案选E,怎么也想不明白。。。