Going by whether one term is the opposite of the other, which one of…

The correct answer is Option (3) → Secularism and protection of minorities

Option (1) Secular and communal — Incorrect. Secular and communal are opposites in everyday Indian usage. A secular person or state favours no religion, and a communal one puts its own religion above others.

Option (2) Mandatory obligation and voluntary personal practice — Incorrect. These two are opposite forms of religion in western history. Secularisation turned religion from a mandatory obligation into a voluntary personal practice.

Option (3) Secularism and protection of minorities — Correct. Secularism and protection of minorities are not opposites. The Indian state holds both commitments at the same time, and the pull between them has caused complications, such as the charge of appeasement.

Option (4) Authoritarian state and democratic state — Incorrect. An authoritarian state is the opposite of a democratic state. In it the people have no voice and those in power answer to no one.