**Core Concept**
The period of isolation for Measles is a critical public health measure to prevent transmission of the virus, primarily affecting individuals with weakened immune systems, such as young children and those with chronic illnesses. Measles is a highly contagious viral disease caused by the Measles virus, belonging to the Paramyxoviridae family. The virus is transmitted through respiratory droplets, direct contact with infected individuals, or contaminated surfaces.

**Why the Correct Answer is Right**
The recommended period of isolation for Measles is typically 4 days after the onset of the rash, when the individual is most contagious. This period is chosen because the virus is present in high quantities in the respiratory tract during the prodromal phase (1-4 days before the rash appears) and the early phase of the rash (0-4 days). After 4 days, the virus load decreases significantly, reducing the risk of transmission. It's essential to note that the exact timing may vary depending on the individual's symptoms and the presence of any complications.

**Why Each Wrong Option is Incorrect**
**Option A:** This is an incomplete answer and does not provide a specific duration for isolation.
**Option B:** This option is incorrect because it does not accurately represent the recommended period of isolation.
**Option C:** This option is also incorrect as it is a shorter duration than the recommended period of isolation.

**Clinical Pearl / High-Yield Fact**
It's crucial to remember that the period of isolation for Measles is critical in preventing the spread of the virus, especially in high-risk populations. Healthcare workers and caregivers should be aware of the incubation period and the contagious period to take necessary precautions and prevent transmission.

**Correct Answer:** C. 4 days