**Core Concept:** Smallpox is a highly contagious viral disease caused by the variola virus, which was once a major global health concern but was successfully eradicated through a combined effort of vaccination campaigns and surveillance.

**Why the Correct Answer is Right:** The World Health Organization (WHO) successfully declared the global eradication of smallpox on **Dec 8, 1980**. This achievement was made possible due to the combined efforts of governments, healthcare workers, and the public's participation in vaccination campaigns, particularly the vaccination program led by Dr. Albert Sabin. The eradication involved close monitoring and reporting of any suspected cases, which led to the elimination of the virus globally.

**Why Each Wrong Option is Incorrect:**

A. **Dec 8, 1977**: While this is the date when the World Health Assembly endorsed the Smallpox Eradication Programme, the eradication was declared on Dec 8, 1980, not 1977.
B. **Dec 8, 1980**: This date is incorrect as well. The eradication was declared on Dec 8, 1980, not the year 1980.
C. **Dec 8, 1978**: This date is also incorrect. The eradication was declared on Dec 8, 1980, not in 1978.
D. **Dec 8, 1979**: The eradication was declared on Dec 8, 1980, not in 1979.

**Clinical Pearl:** The eradication of smallpox serves as a significant milestone in global public health efforts, demonstrating the power of coordinated international cooperation and the importance of sustained vaccination campaigns for infectious disease control.