I want to become a software engineer but I'm not certain about a subject I chose. What do I do?

I want to study software engineering and I'm not sure about my subjects. So basically at my school we have 4 streams and you can only chose 1 subject in each. I chose pure mathematics, physical sciences, tourism and business (my school does not offer CS, IT or CAT). The problem is that some people are advicing me to not chose tourism and to instead do either accounting or life sciences (other subjects in the stream). I don't want to do either since tourism is the easiest in the stream I want to make sure I have a high APS score. What should I do?