Right to not state my religion

Hi Guys, Recently while applying online for an examintaion for a position in a wholly govt. owned company, i was asked to state my religion , apart from the usual OBC/General question. The question was mandatory, and although there was an 'other' option, it further needed to specify which 'other' religion. Although i am aware the Govt. of India doesnt recognise non-religion as of now, i was under the impression that nowhere would we be required to mandatorily state our birth religion, not least for Govt. job applications when we are already made to the select the "category" . The examination is question is http://ibps.sifyitest.com/niaastoct14/. As i had applied on the very last day, the page is now down and i am unable to give you a screen shot. My question is, however, are they really within their rights to manatorily make us reveal our birth religion when no practical purpose is served by it? Also, is there any legal way in which i can abstain from stating my religion in the future?