Hello,

You can check if there is " others " option in the registration form. If there is then you can select others option else you have to make an enquiry in the institute . CBSE is National board and there should be this option and due to introduction for changes,they haven't updates the website.

you can even put a mail to the board regarding the same problem. Better to ask at your institute about it and what to fill there.

Hope it helps!