You are listing the tasks you still have, so B is the most logical since it describes both items as equal tasks you still have to do. A doesn't make any sense because the although clause indicates that even though you have music you still have so much homework. It would make sense if the two sentences given had anything indicating that the two were supposed to be contradicted and not listed. C doesn't fit in this context because the word "so" implies that you have to learn the music because you have a lot of homework. It isn't logical. D doesn't fit either because the word "yet" tells us that the two are contrasting each other, which is not what is happening in the given sentences.
