Answer:
a. a beast cruel and monstrous.
Step-by-step explanation:
This is the description that would best fit Cerberus. Cerberus is a multi-headed monster that guards the Underworld according to Greek mythology. Cerberus is first described in Hesiod's Theogony, although he continued to appear in various Greek, Roman and Byzantine sources. Cerberus is particularly well-known because his capture was one of Heracles's twelve labors.