The answer to this question is option A: his self adoration. This is what refers to the flame that consumes Narcissus based on the given passage above. In the Greek Mythology, Narcissus is a hunter who is known for his ultimate beauty and many admired and fell in love with him. One time, he saw his reflection in the water. Because of how handsome he is, he fell in love with his own self that even the nymph Echo could not stop him from his self adoration.
"With this, and much more of the same kind, he cherished the flame that consumed him, so that by degrees he lost his colour, his vigour, and the beauty which formerly had so charmed the nymph Echo." In this passage, the flame consuming Narcissus refers to A. his self adoration. B. his love for Echo. C. his regret for treating the nymphs poorly. D. his punishment from Hera.