High Yield Topics

Could someone please tell me what the highest yielding topics in IGCSE Maths, Biology and Chemistry (all extended) are.

I don't know much about igcses, sorry, but from my knowledge cell biology in general (like transport, specialised cells, etc.) is important for biology and for maths I think algebra is one of the most expanded topics, meaning that algebra can be applied to many questions so they may come up.