Which one of the following is correct statement regarding small pox?

The correct option is D It is an air borne disease, caused by droplet infection of variola virus.
Smallpox is a highly contagious viral disease. It is an air-borne disease which spreads via the droplets infected with Variola virus which is most complex of the orthopoxvirus genus, having many different strains. The patients are symptomized by high fever, rashes all over the body, nausea etc.

Hence, the correct answer is 'It is an airborne disease, caused by droplet infection of variola virus'