The correct option is D The Kalinga kingdom had flourishing trade relations with South East Asia because of the numerous ports in the region. The trade would be a good source of revenue for Ashoka, once Kalinga was conquered.
Kalinga, located on the eastern coast of India had lots of ports. The ports could be used for trade and more wealth could be accumulated in this way. This may have been one of the reasons for Ashoka's decision to conquer Kalinga.