The correct option is D They believed that only birth could make a person untouchable.
Many prominent vachanakaras were a part of Basavanna’s Anubhava Mantapa. The vachanakaras used their Vachanas as a means to identify and address the problems inherent in the society of their times. They preached that all humans are equal and that no one is untouchable by birth and that only profane thoughts and behaviour made a person untouchable.