**Core Concept**
The Rabies vaccine schedule of 0,3,7,14,30,90 is a widely accepted regimen for post-exposure prophylaxis (PEP) and pre-exposure vaccination. This schedule is designed to provide adequate immunity against the rabies virus by stimulating an immune response in the body.

**Why the Correct Answer is Right**
The correct answer represents the day of the first dose, which is crucial for initiating the immune response against the rabies virus. The Rabies vaccine is a live, attenuated vaccine that induces both humoral and cellular immunity. The initial dose (day 0) is essential for stimulating the immune system, and subsequent doses are administered to boost and maintain the immune response. The correct schedule ensures timely and effective protection against rabies infection.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect as it does not represent the correct day of the first dose in the standard Rabies vaccine schedule.
**Option B:** This option is incorrect as it is not the correct day of the first dose, and it may not provide adequate immunity against the rabies virus.
**Option C:** This option is incorrect as it does not represent the correct day of the first dose in the standard Rabies vaccine schedule and may not stimulate an effective immune response.

**Clinical Pearl / High-Yield Fact**
It is essential to note that the Rabies vaccine schedule may vary depending on the patient's risk category, age, and health status. A healthcare professional should always assess the patient's individual needs and adjust the vaccination schedule accordingly.

**Correct Answer: C. Day of first dose.**