An elongated hyphen is a more formal way of introducing excess information by means of interjection. It’s only allowed if the information being supplied is critical to the text it interrupts.
The correct choice is D, where the text contained between the hyphens adds extra detail to the sentence. With the inclusion, we now know that Andrew will have to work extra hard to learn the guitar, because he doesn’t know how to read music in the first place. Choice B needs commas instead of hyphens, as it’s introducing a list. Choices A and C need to omit their hyphens entirely.
