**Core Concept:** World Health Day is an annual event organized by the World Health Organization (WHO) to promote global health and raise awareness on specific health-related themes.

**Why the Correct Answer is Right:** The correct answer is **Option C: 7th April**. This is the day when the World Health Organization (WHO) was founded in 1948. Celebrating World Health Day on this date allows it to mark the organization's establishment and its commitment to improving global health.

**Why Each Wrong Option is Incorrect:**

**Option A (4th April):** This date is too early and does not connect with the founding of the WHO.

**Option B (10th April):** This date is also incorrect as it does not align with the WHO's foundation anniversary.

**Option D (17th April):** Although this date might seem relevant, it is unrelated to the WHO's history or achievements.

**Clinical Pearl / High-Yield Fact:** The WHO focuses on improving health outcomes, promoting research, and providing technical support to countries to develop health systems, ensuring global health security, and addressing health emergencies.

**Correct Answer: .** 7th April