Correct Answer: Religion, race, caste, sex, place of birth
Core Concept: Prohibition of Discrimination under Article 15
Detailed Breakdown: Article 15(1) directs that the State shall not discriminate against any citizen on grounds ‘only’ of religion, race, caste, sex, place of birth, or any of them. The word ‘only’ implies that discrimination on other grounds (like residence, language, or income) is not prohibited. Articles 15(3) to 15(6) provide exceptions, enabling the State to make special provisions/reservations for women and children, socially and educationally backward classes (OBCs), Scheduled Castes (SCs), Scheduled Tribes (STs), and Economically Weaker Sections (EWS).
📖 Source: M. Laxmikanth, Indian Polity (7th Ed.), Chapter 7: Article 15