Trairupya three marks of hetu – UGC NET Question

Trairupya refers to the threefold set of criteria that any acceptable hetu must meet: it must occur in the paksha, be present wherever the sadhya is present and be absent where the sadhya is absent. Together, these conditions ensure that the proposed reason is reliably connected with the probandum. Nyaya uses trairupya as a rigorous test for evaluating potential middle terms.

Option A:
Option A, upadhi, is a limiting condition that reveals hidden restrictions on a supposed vyapti, but it is not itself the positive set of requirements for a valid hetu.

Option B:
Option B, vyapti, denotes the universal concomitance between hetu and sadhya but does not specify the distinct checks needed to see whether a particular hetu instance exemplifies that relation.

Option C:
Option C is correct because trairupya literally means "having three forms" and is explicitly formulated in Nyaya as the standard yardstick for judging the soundness of reasons in inference.

Option D:
Option D, hetvabhasa, refers to fallacious reasons that fail to meet one or more of these marks and is therefore a class of defects, not the criteria themselves.