**Core Concept**
John Snow is considered the Father of Modern Epidemiology and Public Health, and his work is closely associated with the prevention and control of a major infectious disease outbreak. Snow's efforts led to significant improvements in public health practices and the development of modern epidemiology.

**Why the Correct Answer is Right**
Cholera is a bacterial infection caused by Vibrio cholerae, which was a major public health concern in the 19th century. John Snow's work in London in 1854, where he identified the source of the outbreak and advocated for the removal of a contaminated water pump handle, is a pivotal moment in the history of public health. Snow's investigation and subsequent removal of the pump handle led to a dramatic reduction in cholera cases, demonstrating the importance of epidemiological investigation and intervention in controlling infectious disease outbreaks.

**Why Each Wrong Option is Incorrect**
**Option A:** Malaria is a mosquito-borne disease that was also a major public health concern during the 19th century, but it is not specifically associated with John Snow's work.
**Option C:** Tuberculosis is a bacterial infection that was prevalent during the 19th century, but it is not linked to John Snow's contributions to public health.
**Option D:** Plague is a bacterial infection caused by Yersinia pestis, which was also a significant public health concern during the 19th century, but it is not associated with John Snow's work.

**Clinical Pearl / High-Yield Fact**
John Snow's work in identifying the source of the cholera outbreak and advocating for its removal is a classic example of the importance of epidemiological investigation in controlling infectious disease outbreaks. This event marked a significant shift in public health practices, emphasizing the need for evidence-based decision-making and the importance of removing sources of infection to prevent disease spread.

**✓ Correct Answer: B. Cholera**