The long flashback early in Book 1 of the Iliad explains why...?

wow this is a tough question. It really could be A or D. But I'm leaning towards it being A. Because the flashback starts with Agamemnon dishonoring Apollo by stealing Chryseis. Then her father calls on Apollo to send down a plague...so the flashback would be explaining why soldiers were dying. It doesn't really explain why Agamemnon chose Chryseis as a war prize other than obvious reasons.