Which one of the following pairs does not form part of the six systems of Indian Philosophy?

Option (C) is correct because Lokayata (a materialistic school) and Kapalika (a tantric Shaivite sect) are heterodox or sectarian traditions that fall outside the "Shad-darshana," the six orthodox systems of Indian philosophy. Options (a), (b), and (d) are incorrect as they represent the three complementary pairs—Mimamsa-Vedanta, Nyaya-Vaisheshika, and Sankhya-Yoga—that constitute the classical orthodox schools. The core concept tested is the classification of Indian philosophy into *Astika* (orthodox) schools that accept Vedic authority versus *Nastika* (heterodox) schools.