What is the main theme of this poem?
Life is relatively short, so you should enjoy the world's beauty while you are able.
The poet conveys that life is short, and travels rapidly by. The only thing a person can do is relish each moment that he has. Nature will go on whether one enjoys it or not. Nature is indifferent to man and does not wait for a man to enjoy its loveliness. The speaker will appreciate the spring and the exquisite trees as long as he walks the earth. Hence the correct answer is option A.