Step 1: Understanding the Concept:
The question asks about the dual identity of the protagonist, Charudatta, in the Sanskrit play \textit{Mrichchhakatika} ("The Little Clay Cart").
Step 2: Detailed Explanation:
Charudatta, the hero of the play, is a man of great virtue who has fallen into poverty due to his excessive generosity. The play clearly establishes his social identity in two ways:
By birth, he is a Brahmana.
By profession, he was a wealthy merchant and the leader of a trade guild or caravan. The term for such a merchant is a Sarthavaha.
The other options are incorrect:
Nishada refers to a forest-dwelling tribal community.
Kshatriya is the warrior or ruling varna.
Mlechchha refers to a foreigner or an outsider.
Step 3: Final Answer:
Charudatta was described as a Brahmana by birth and a Sarthavaha (merchant) by profession.