I would choose a. Simply because the author talks about it as if it's all that really ever existed and that nature cannot take over what it is not. However, it goes on about seeing how erosion and rot can affect such things and tries to compare it to things in nature as if it were nature itself.
Answer:
A. As the sun set over the ocean, the water appeared very beautiful.
I think the mood is mystic, excitement, and hope.
