The correct answer is (b), smallpox.
Diphtheria is a highly contagious bacterial disease that affects the throat and nose. It can cause serious complications, including death. Chickenpox is a viral disease that causes a characteristic rash. It is usually a mild illness, but can be serious in some people, such as pregnant women and people with weakened immune systems. Smallpox is a viral disease that causes a severe rash. It was once a common and deadly disease, but it has been eradicated worldwide.
India was declared smallpox-free in 1977. This was achieved through a successful vaccination campaign that reached all parts of the country. The last case of smallpox in India was reported in 1975.
Diphtheria and chickenpox are still present in India, but they are much less common than they used to be. This is due to the widespread use of vaccines.
In conclusion, the only disease that has been eradicated in India is smallpox. Diphtheria and chickenpox are still present in India, but they are much less common than they used to be.