I agree with the person above - I believe the correct answer is A. serenity.
Thoreau was a transcendentalist, which means that he wrote about nature quite a lot. He believed that people should return to living in nature and escape from the concrete cities they were surrounded with in order to find their true selves once again. His description of the pond during the night and day creates a serene and peaceful picture one could relax to.
The vES ending should be added to nouns that end in -f or -fe in their singular form. In that case, the -f or -fe is removed and -ves is added as a plural ending. Examples include: life - lives, wife - wives, knife - knives, wolf - wolves, leaf - leaves. But there are also exceptions, such as belief - beliefs, cliff - cliffs, roof - roofs.
The figurative language used in this sentence is a metaphor because in this sentence it is saying what something is without using like or as.
The subordinate clause in this sentence is 'Since I stopped vacuuming', and it is used as an adverb in this sentence, the adverb of time.
