The correct answer is: C. an antibiotic.
Penicillin is a type of antibiotic that is used to treat bacterial infections. It works by stopping the bacteria from growing. Penicillin is one of the most widely used antibiotics in the world. It is effective against a wide range of bacteria, including those that cause pneumonia, meningitis, and scarlet fever.
Antiseptics are substances that are used to kill or prevent the growth of bacteria on the skin. They are often used to clean wounds and cuts. Disinfectants are substances that are used to kill or prevent the growth of bacteria on surfaces. They are often used to clean surfaces in hospitals and other healthcare settings. Insecticides are substances that are used to kill insects. They are often used to control pests in homes and businesses.
Penicillin is not an antiseptic, disinfectant, or insecticide. It is an antibiotic.