Consider the following diseases:

Correct Option (b):

Smallpox is the only disease among the given options that has been officially eradicated from India. The World Health Organization (WHO) declared India free from smallpox in 1977, following a global eradication program that involved extensive vaccination efforts. Diphtheria, although largely controlled through routine immunization, still records cases and occasional outbreaks in various regions. Chickenpox is a common infectious disease that continues to occur sporadically across India and has not been eradicated.

Incorrect Options:

• Option (a) is incorrect because Diphtheria and Chickenpox have not been eradicated in India; they continue to persist.
• Option (c) is incorrect as only Smallpox among the listed diseases has been eradicated, not all three.
• Option (d) is incorrect because Smallpox has indeed been eradicated from India, making the statement "None" false.