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.
Typically he leaves the stage. That is the Protagonist's role during the First Stasimon. Option D is correct.
A stasimon in Greek tragedy is a stationary song, composed of strophes and antistrophes and performed by the chorus in the orchestra.
According to Aristosteles, each choral song (or melos) of a tragedy is divided into two parts, first the parodos (Ancient Greek: πάροδος) and then the stasimon.
To protect it's surroundings