When penicillin was first introduced, it was very effective in destroying most of the bacteria that cause gonorrhea. Today, certain varieties of this
bacterium are resistant to penicillin. Which statement best explains the
appearance of these resistant varieties?
A. Penicillin stimulated the bacteria to become resistant, and this
resistance was passed to the offspring.
B. Penicillin today is not as strong as the penicillin used when it was first
introduced.
C. Penicillin stimulated the production of antigens in the resistant
bacteria.
D. Penicillin killed the susceptible bacteria, while naturally resistant
varieties survived and reproduced.