Concept:
Mauryan Emperor Ashoka was the first Indian ruler to issue royal edicts engraved on stone pillars and rocks. His principal motivation was to propagate his philosophy of \textit{Dhamma} across his vast kingdom.
Step 1: Verifying Assertion (A)
While high-class literature of ancient times was largely recorded in Sanskrit, the vast majority of Ashokan inscriptions found across the core regions of his empire were composed in the Prakrit language (written mostly in the Brahmi script). Hence, Assertion (A) is true.
Step 2: Verifying Reason (R)
Prakrit was the lingua franca or the spoken vernacular tongue of the common people during the Mauryan period. Ashoka explicitly chose to publish his moral code and state rules in Prakrit so that ordinary citizens could easily read, comprehend, and follow his messages without the need for elite priestly mediation. Hence, Reason (R) is true.
Step 3: Determining the causal link
Why were most inscriptions written in Prakrit? They were written in Prakrit precisely because Ashoka intended to communicate effectively with the local common populace. Therefore, Reason (R) provides the direct and correct explanation for Assertion (A).