Final answer:
The answer is C. Narrow, as drugs with a narrow therapeutic window have a small range between therapeutic and toxic doses, requiring close monitoring to avoid toxicity.
Step-by-step explanation:
Drugs with a narrow therapeutic window require close monitoring for toxicity. The correct answer to the question is C. Narrow. A therapeutic window refers to the range of drug dosages which can treat disease effectively without having toxic effects or causing harm. When a drug has a narrow therapeutic window, it means that the range between the minimum effective dose and the toxic dose is quite small, necessitating precise dosing and often, close patient monitoring to ensure safety. Drugs with a wide therapeutic window have a larger range and thus pose less risk for toxicity, making frequent monitoring less critical.