Option 1: Dhammaguru - This option refers to a teacher or guru of Dhamma. While it is possible that Ashoka may have appointed Dhammagurus to teach people about Dhamma, there is no specific mention of this in the question.
Option 2: Dhamma yogi - This option refers to a practitioner of Dhamma. It is unlikely that Ashoka appointed practitioners to teach others about Dhamma.
Option 3: Dhamma acharya - This option refers to a teacher or instructor of Dhamma. Again, while Ashoka may have appointed Dhamma acharyas, there is no specific mention of this in the question.
Option 4: Dhamma mahamatta - This option refers to officials appointed by Ashoka to teach people about Dhamma. This is the correct answer provided in the question. Dhamma mahamattas were officials responsible for spreading the teachings of Dhamma and ensuring that the people understood and followed them.