Sir,
I am appearing for an interview for the first time in WIPRO BPO.
What shall I answer when they ask why shall we hire you?

You need to sell yourself, what makes your talents and experience better than anyone. No one can answer that question except for you. I would suggest making a list of everything that makes you... well you. From your work ethic, to personal experiences, to your education. Then use these in your interview to set you apart from the rest of the pack. Good luck.