单选题 According to Greek mythology, the goddess Eris inscribed "to the fairest" and tossed in the midst of the feast of the gods at the wedding of Peleus and Thetis, thus sparking a vanity-fueled dispute among Hera, Athena, and Aphrodite that eventually led to the Trojan War. Thus,
"______ of discord" is used to signify the core, kernel, or crux of an argument, or a small matter that could lead to a bigger dispute.