If l had take science and l have got 88 merit marks in PCM subject so which field I can select l am comfortable with all fields.

Based on your score it is clear that you can get a good college in Delhi university. If you want to do bsc in any physics chemistry or maths you can do it from a naming college but it also depends on your category. In du you can get admission from your merit score.
But in the field of engineering your marks will not work at all. You need to score a good marks in jee.
So first choose what you want to be in your life.
Btech is basically have more scope than the bsc so you may go according to your desires.