I didn't think you are allowed to pick up EE1 at the start of Yr 12. Nevertheless, I agree with Harkaraj's examples - a friend of mine did modern+ancient+ext history, and did brilliantly. Why not take all the science subjects if you are interested in science and, most importantly, are good at these subjects? I understand your concern because I actually had similar concerns around the time of subject selection, so I didn't choose physics. That was perhaps my biggest regret throughout senior high school.