The correct option is C Ashoka used his military to invade other countries and spread the message of Dhamma.
Ashoka devoted his life to ahimsa (non-violence) after the Kalinga war. To spread the message of Dhamma, Ashoka made inscriptions on rocks and pillars about Dhamma. He conducted royal tours known as Dhamma-yatras. He also took up Public welfare activities known as Dhamma-mangala to spread the message of Dhamma.