The answer is: C. there is a triad of great gods known only to those who attain enlightenment
Buddhism is a polytheism religion. The followers of Buddhism believed that there are more than one Gods in this universe that serves their own function to the world.
This triad of great gods could only be known if humans achieve enlightenment where they've completely disregard their needs for materialistic things in life. Buddha taught that even though this extremely difficult, it is possible for anyone to achieve enlightenment within one lifetime.