Root = act, that your answer to what are is the root of enactment
So if you think about the connotations of the words, veils conceal things, sifting implies a kind of search, so I'd say the answer is C. a ghostly, mysterious mood.
Answer: B
Reason: A is an example of symbolism. C is describing a plot line, and D is completely irrelevant in regards to the question being asked. B is teaching a lesson, which is a theme.
C it contains facts about a topic