Explanation

Kautilya's Arthashastra lays down the king's duty (rajadharma) and the norms governing conquest and administration of acquired territory, enjoining the conqueror to uphold and establish dharma — the righteous moral and social order — in the conquered land rather than ruling by mere force. The text's framework for legitimate kingship is centred on dharma, not specifically on varna distinctions, religious uniformity, or abstract justice detached from dharma. Hence 'dharma' is the correct answer.