Dear Neha, you will choose your Nationality as Indian. Cos you have been abroad for studies, your Nationality will still remain Indian. PIO is someone like:

1. Any person who has ever held an Indian passport, or
2. The person's parents, grandparents or great grandparents were born in and were permanent residents of India and never moved to (i.e., were never nationals of) Bangladesh and Pakistan, or
3. The person is the spouse of a citizen of India or of a PIO and has been so for two years or more, and
4. The person and his/her parents, grandparents or great grandparents must not have been a national of Bangladesh or Pakistan at any point of time