Detailed Solution:
The correct answer is “Kekaya”.
King Asvapati of the Upanishadic period ruled the Kekaya kingdom, which was located on the banks of the Beas river, east of the Gandhar kingdom. Asvapati was also a well-known teacher of the time and had a daughter named Kaikeyi, who later became the queen of King Dasharatha, and seven sons.