C. Beauty can be alluring, but it is also dangerous.
Explanation:
This is the statement that best describes the theme. In these lines, Christina Rossetti discusses the essence of beauty. She states that beauty can be alluring, as it wooes and excites her. However, she also highlights the dangers that beauty comes with. We learn about this when the author tells us about the same object of adoration turning "loathsome" and "foul."
If a king rules his subjects with nothing in mind about his subjects' welfare, he will not care about what happens to the people, and whatever happens is none of his business which is a sign of tyranny.
