First of all it must be clear that in which subject you want to do Bsc. Because for doing Bsc. in pure science subjects like in chemistry and physics your percentage of PCM in 12th board exam will be the major factor. For doing BSc. hon. In Zoology and Botany your PCB score will be counted. For doing Bsc. in Maths your percentage in Pcm +one language will be counted.For doing Bsc. in computer science your PCM + your computer science marks will be the major factor