hmmm .... for those who'd go with E could you say why ?
[Ok i just started the SC stuff and this is my first post in the category so be gentle
I'd go with D) because: There are contrasting ideas here (you can choose music but you can't choose 'no music') so we need conjuctions(or conjuctive adverbs) such as "however", "although" or "but"
so C) and D) and E) make the first cut.
C) is wrong because it compares music with slopes
E) is wrong because it uses the coordinating conjuction 'but' which can only be used to join grammatical structures that are similar. In this case since a comma is used before the' but' and there is a 'clause' before it .... there should be also be a 'clause' after it. E) puts a phrase there and so is wrong.