Final answer:
In Aeschylus' Prometheus Bound, Hera punishes Io for sleeping with Zeus by transforming her into a cow and sending a gadfly to torment her.
Step-by-step explanation:
In Aeschylus' Prometheus Bound, Hera punishes Io for sleeping with Zeus by transforming her into a cow and sending a gadfly to torment her. Io is forced to wander the earth, constantly pursued by the gadfly and enduring great suffering. This punishment is a result of Hera's jealousy and anger towards Zeus and Io. Hera's actions demonstrate her power and ability to exact revenge on those who betray her.