Correct answer: A. Royal status and authority
Explanation: The direct answer is A: royal status and authority. Rajasuya was an important Vedic royal sacrifice connected with the position and power of a king. It was not simply an ordinary religious act; it helped a ruler display high status, receive recognition and assert authority over other rulers or groups. The reasoning is: the ritual was performed by a king; royal rituals expressed political standing; recognition and prestige strengthened kingship; therefore Rajasuya is associated mainly with royal authority. A is correct. B, cotton trade, concerns commerce and production, not the main meaning of this Vedic sacrifice. C, Buddhist monastic rules, belong to the organization and discipline of Buddhist monks, whereas Rajasuya belongs to the Vedic royal tradition. D, Harappan drainage, concerns urban engineering and sanitation in the Indus cities, many centuries and a different context apart. Exam cue: remember Rajasuya as a ritual of Vedic kingship, prestige and political power. The supplied answer is accurate.