**Core Concept**
Measles, Mumps, and Rubella (MMR) vaccine is a live, attenuated vaccine administered to protect against these three infectious diseases. The vaccine schedule is crucial to ensure adequate immune response and prevent outbreaks.

**Why the Correct Answer is Right**
The MMR vaccine is typically administered at 12-15 months of age, as part of the routine childhood vaccination schedule. This timing allows for the development of adequate immunity against measles, mumps, and rubella, while also considering the risk of exposure to these diseases in early childhood. The Centers for Disease Control and Prevention (CDC) and the World Health Organization (WHO) recommend the MMR vaccine be given at 12-15 months of age.

**Why Each Wrong Option is Incorrect**
**Option A:** Bih - This option is not a valid time for MMR vaccination, and the term "Bih" is unclear or possibly a typo.
**Option B:** 6th month - Administration of MMR vaccine at 6 months of age is not recommended, as it may interfere with the maternal antibody response to measles and rubella.
**Option C:** One year - While close to the correct answer, the recommended age for MMR vaccination is slightly older, typically between 12-15 months.

**Clinical Pearl / High-Yield Fact**
The MMR vaccine is a live, attenuated vaccine, meaning it contains weakened forms of the measles, mumps, and rubella viruses. This live attenuated nature allows the vaccine to induce a strong immune response, but also requires careful handling and storage to prevent accidental exposure.

**✓ Correct Answer:** D. 11/2 years