The correct option is C clarity
Ambiguity means the quality of being open to more than one interpretation; inexactness. The opposite of ambiguity is clarity, or the quality of being coherent and intelligible. Hence, Option C is correct. Among the rest of the options, perversity means a deliberate desire to behave in an unreasonable or unacceptable way; contrariness, rationality means the quality of being based on or in accordance with reason or logic, certainty means firm conviction that something is the case. These options do not express the intended antonym, hence incorrect.