No its not ok to add BC certification in lieu of OBC certification as rrb NTPC clearly defines the rules of obc certificate which states the certificate have to be issued by a certified authority, such as a District Justice of the peace, Collector, Deputy Commissioner, or Income Officer and https://railwayrecruitment53959.worldblogged.com/39466129/railway-recruitment-bangalore-last-date-rrb-apply