I would think the answer was B but I’m not entirely sure.
Hope this helps
Answer:
A: To act as the subject of the main clause
The theme of this is the idea that all the actions which you do to try to determine the aesthetic of a poem is vain if you in any way feel the need to manipulate it or even try to interpret it -- it is its own being. It is a complex, incalculable demonstration of beauty.
