UPSC 2024 Prelims asked a simple yet high-concept science question: Which compound dilates blood vessels and increases blood flow in the human body? The correct answer is Nitric Oxide, a gas that plays a key role in cardiovascular health by relaxing blood vessels, allowing smoother circulation. Such science-based conceptual questions are common in UPSC, especially in Prelims. This is your reminder to never neglect the basic science concepts. Follow ZenStudy for daily UPSC-oriented MCQs, notes, and explanations that make cracking Prelims a smart and consistent process. Prepare smartly, not just hard.