In the book of Obadiah, a prophecy is given against Edom. What fundamental sin of Edom led to this prophetic condemnation?

A Edom's idolatry and worship of false gods. B Edom's economic exploitation of Israel through unfair trade practices. C Edom's refusal to allow Israel to pass through their land during the Exodus. D Edom's rejoicing and taking advantage of Judah's distress during its invasion and subsequent downfall.