Correct Answer: (a) Rig Veda
Note: The 'Varnas' have been known from Rig Veda since a hymn in the Rig Veda portrays the Brahmin (Priest), the Kshatriya (noble), the Vaishya (commoner) and the Shudra (servant) issued forth at creation from the mouth, arms, thighs and the feet of the primeval person (Purusha). Although the literal meaning of the word Varna is colour or class (in Sanskrit).