Choice A is the best answer. The convention being tested is punctuation between a preposition and its complement. No punctuation is needed between the preposition “of” and its complement, the noun phrase “healing, self-discovery, and memory.”
Choice B is incorrect because no punctuation is needed between a preposition and its complement. Choice C is incorrect because no punctuation is needed between a preposition and its complement. Choice D is incorrect because no punctuation is needed between a preposition and its complement.