Final answer:
Selective toxicity ensures an antimicrobial is harmful to a pathogen, not the host, by exploiting metabolic and structural differences. The correct answer is 'A and C,' meaning both metabolic and structural differences are utilized.
Step-by-step explanation:
Selective toxicity refers to the ability of an antimicrobial drug to harm the target microbe without harming the host. To achieve this, antimicrobial agents take advantage of metabolic and structural differences between the host (e.g., human cells) and the pathogen (e.g., bacteria, viruses, fungi, protozoa).
It is incorrect that to be effective, an antimicrobial agent must be more toxic to the patient than the pathogen. In fact, the opposite is true; a selectively toxic drug must be more toxic to the pathogen than the host. Thus, the correct answers regarding selective toxicity are that it takes advantage of metabolic differences between host and pathogen (A) and structural differences between host and pathogen (C).
The correct answer to the student’s question is therefore ‘E) A and C’.