The answer is: A
Explanation
The correct option is A: Sex.
According to Article 15(1) of the Indian Constitution, the state shall not discriminate against any citizen on grounds only of religion, race, caste, sex, place of birth or any of them. This means that discrimination based on sex alone would be violative of Article 15(1), but discrimination based on sex and other grounds, such as caste or religion, may not be violative of Article 15(1). For example, a law that prohibits women from entering a temple would be violative of Article 15(1), but a law that prohibits women of a certain caste or religion from entering a temple may not be violative of Article 15(1), depending on the context and justification of the law.