Which of the following issue is the most contentious of all aspects of cultural diversity in India?

religion-based identities

The correct answer is Option 4: religion-based identities

NCERT: Perhaps the most contentious of all aspects of cultural diversity are issues relating to religious communities and religion-based identities. These issues may be broadly divided into two related groups – the secularism communalism set and the minority–majority set. Questions of secularism and communalism are about the state’s relationship to religion and to political groupings that invoke religion as their primary identity. Questions about minorities and majorities involve decisions on how the state is to treat different religious, ethnic or other communities that are unequal in terms of numbers and/ or power (including social, economic and political power).