hello aspirant,

see in science stream it is mandatory to take physics, chemistry,  mathematics. and in optional you can take biology/computer science/ statistics etc. so i suggest you to study physics, mathematics with very concentration as you express your wish to study electrical engineering. to get any competitive exam for engineering questions will be ask from pcm. so study well. and one thing i should include if you decided that you have to come in engineering, it is better to take computer science or statistics as your fourth subject.