The answer is: letter B, The falling out between Achilles and the son of Atreus.
Explanation:
The conflict that happened between "Achilles" and "Agamemnon" (the son of Atreus) boils down to a woman named "Briseis." Briseis was a concubine war prize for Achilles after the Trojan war. In the story of Iliad, Agamemnon was forced by Apollo to give up Chryseis (Agamemnon's slave). As a reward to giving up her slave, he demanded that Briseis should be rewarded to him. This angered Achilles because Agamemnon was stripping him of his reward. Thus, this caused a war between them that killed many lives.
Clearly, the opening to Homer's Iliad shows the falling out between Achilles and Agamemnon (the son of Atreus).
