They can ADVISE you on your chosen subjects but, unless you intend to do something in the biology,chemistry or biochemistry field, then the first two DON'T MIX with the second two.
What is it you want to do exactly?
Don't let your parents chose your subjects for you, it is your life (your A levels and degree will open doors for you but close so many more, i.e. no history, music, religious studies etc... but will open up doors in the relevant fields).
My mother advised me to do the following GCSE options (Business BTEC, ICT and Double Science), the only useful one of those I liked was science and the business and IT complimented each other.
In short, try and chose subjects which will mix/compliment each other nicely.
Back on topic, what degree/job do you want to do exactly?