Hii Venkata!

In general, if you apply for any entrance examination all over India, you need to specify the category from which you belong. You are provided reservations accordingly. But, for this, you should have the proof of it with it, that is, the caste certificate or the affidavit. Same is the case here. If you enter your details as BC-D category and want a reservation, you should be able to produce the proof for it, the exact certificate for it. If you can't, you are not provided the benefit. You are considered general category candidate.

Hope you understand.

Good luck!