Biology Spl

No one can actually tell you that how you have to chose your stream . It is completely your decision. It depends on your interest and will. You can choose any of the career in these subjects. All of these have immense scope.
However if you are willing to go in anyone of them then you can consider various factors like jobs available, salary offered etc.
In engineering you can get job faster than in medical. But nowadays it is difficult to get a job as the number if engineers is huge. Medical filed almost guarantees you a job but you have to work harder and for longer than in engineering. For computer science you can do engineering or may be masters. Maths can be chosen as a separate career in itself. You can do masters and go for teaching line.
At the end it depends all on you and your interest. You have to decide what is good for you and how much you can work for it. Your hard work and willingness will matter more than the course you choose.
Hope it helped;)