While often remembered for his role in advising King David, what unique skill did Ahithophel possess that made his counsel so highly valued?

A He was a skilled military strategist, known for his innovative battle tactics. B He was a gifted diplomat, adept at negotiating treaties with neighboring kingdoms. C His advice was considered as authoritative as if one had inquired of God himself, indicating exceptional wisdom and insight. D He was a renowned physician, capable of healing even the most grievous wounds.