**Core Concept**
The plague, caused by the bacterium Yersinia pestis, is a zoonotic disease with a natural reservoir in rodents. The correct rodent species is crucial for understanding the epidemiology and transmission dynamics of the disease.

**Why the Correct Answer is Right**
Tatera indica, also known as the Indian gerbil, is the natural reservoir of the plague in the Indian subcontinent. These rodents harbor the bacterium in their lymph nodes and spleen, and they can transmit it to other rodents or humans through fleas. The correct identification of the reservoir species is essential for understanding the plague's transmission and developing effective control measures.

**Why Each Wrong Option is Incorrect**
**Option A:** Mus musculus, the laboratory mouse, is not the natural reservoir of the plague. While mice can be infected with Yersinia pestis, they are not the primary reservoir species.
**Option C:** Rattus Rattus, the black rat, is a known vector of the plague but not the natural reservoir. Rattus Rattus can carry infected fleas, which can then transmit the disease to humans.
**Option D:** Rattus norvegicus, the brown rat, is also a vector of the plague but not the natural reservoir. Like Rattus Rattus, Rattus norvegicus can carry infected fleas that can transmit the disease to humans.

**Clinical Pearl / High-Yield Fact**
The plague is a classic example of a zoonotic disease with a complex transmission dynamics involving multiple hosts, vectors, and environments. Understanding the natural reservoir and vectors is crucial for developing effective control measures and preventing outbreaks.

**✓ Correct Answer: B. Tatera indica**