Option b is the correct answer King Asvapati of the Upanishadic Period was the ruler of Kekaya. He was a well-known teacher of the age. The Kekaya kingdom was situated on the bank of river Beas. King Asvapati is a significant figure in the Upanishadic tradition and he is mentioned in several Upanishads, including the Brihadaranyaka Upanishad and the Chandogya Upanishad. He is a reminder of the importance of knowledge and wisdom in the Upanishadic worldview.