As for all other options they are factually wrong, as Buddhism spread across India and Siddhartha Gautama was Buddha's own name so these cannot be true, Confucius never spoke of Buddhism as both of them are probably contemporaries.
The correct choice is "C", "Buddhist missionaries spread the new faith, first to Sri Lanka".
During the second century BC Sri Lanka was converted in the time of Mahinda who was the son of the great Asoka (A legendary emperor who helped Buddhism spread across India and beyond)