In greek mythology, achilles was the son of peleus, a man, and thetis, an immortal sea nymph. thetis wanted her son to be immortal as well, so she dipped him in the river styx. she held him by the ankle, and this was the only part of achilles where he could get hurt. later, achilles fought in the trojan war and died from a wound from an arrow in his ankle. how is the term "achilles' heel" used today? a. it is used to describe people who participate in wars. b. it is used to describe a weakness that might cause the downfall of something. c. it is used to describe people who have overprotective mothers. d. it is used to describe a strength that makes someone invincible.