Antibiotics such as penicillin and streptomycin have been used to treat diseases such as Lyme disease and tuberculosis. Which types of disease-causing organisms can be killed or reduced in number by antibiotics?

A. Both bacteria and viruses respond to antibiotic treatment.

B. Only bacteria respond to antibiotics, and viruses are not affected.

C. Only viruses respond to antibiotics, and bacteria are not affected.

D. Neither bacteria nor viruses are affected by the use of antibiotics.