The correct answer is - C. poor strategies.
Ashoka was a great leader. He was also well educated, and underwent an excellent military training. Ashoka managed to reform the army and of make it by the far the most dominant power in the region. He created a well trained and well equipped army, used elephants in the battles/wars to break the opponent's lines, and there was a great hierarchy in the army where everyone had specific task, and everything was commanded well and in detail with great organization.
This led to a big expansion of the territory during Ashoka's reign, from Afghanistan to the west, to Bangladesh to the east, and from the Himalayas on the north, almost to the southern tip of India, which left the only unconquered piece in the mainland part of the Indian subcontinent.