Which of the following best defines 'selective toxicity' in antimicrobial therapy?

• A. Any chemical that reduces the number of microbes on a surface regardless of effects on human cells
• B. A drug that only targets viral pathogens because viruses are easiest to selectively target
• C. A drug's ability to kill or inhibit a microorganism without causing unacceptable harm to the human host
• D. A compound that indiscriminately kills both microbes and host cells to clear infection quickly

Answer: (C)