Most favorable answer would be
Hindi, but this is not right. Actually, India has NO national language.
India has national flower (Lotus), national animal (tiger), national bird
(Peacock), but in Indian constitution, there is no provision of having national
language, so, there is no national language for India by law.
Article 343 (1) talks about
official languages of India. According to article 343 (1), Hindi and English are
official languages of India.
Suresh Kachhadia has filed PIL
about national language of India. Gujarat High Court has clarified
that, Hindi is not the national language of India.