The Instruction sheet of NPAT available at: https://www.npat.in/docs/Instruction%20Sheet%20for%20NMIMS%20NPAT%202020%20(1).pdf mentions that the dress code shall be strictly smart casuals. Smart casuals means chinos, dark coloured jeans, blazer and a Shirt. T-shirt comes under casuals but not smart casuals. Smart casuals are less formal but still professional. So a T-shirt might not be an option. You may have to wear a shirt or a collared T-shirt.