Yes according to the new on demand policy of NIOS,  students can give examination of mathematics only. You can register for those on the papers for which you have taken admission. This makes the exam flexible and students comfortable and they can give their exams according to their satisfaction. The examination is government certified and eligible in all government and private sectors

Check More: https://www.google.com/url?sa=t&source=web&rct=j&url=https://school.careers360.com/exams/nios-class-12/amp&ved=2ahUKEwjqgsTajsz0AhXcs1YBHem9DeMQFnoECAoQAQ&usg=AOvVaw1qu8_XiZYephZEmr_-8jnq