I believe that there are a number of factors that you should consider if you wish to make an informed decision.
Performance:
Your standard of performance appears to be fairly close across your subjects. Where you know your ranks, subjects where your performance seems favourable are Biology and, to a slightly lesser extent, Mathematics Advanced. Otherwise, your position in Business Studies also seems comfortable. Based on this information, I would suggest that you keep Business Studies as it is likely that you will be able to maintain good performance as you progress through year 12, provided that you commit to regularly studying.
It seems like Chemistry is currently your lowest performing subject, given your yearly exam mark, your overall mark, and your rank, the latter looking the least favourable compared to your ranks in your other subjects. From a performance viewpoint, you may wish to consider dropping Chemistry.
Personal interests:
The fact that you are taking English Extension 2 indicates a level of interest in English, possibly being your favourite subject. In considering your interests, you should recall your experience of taking each of these subjects in year 11. Was there a subject that you enjoyed and/or felt more interested in learning than another? Focusing on subjects that you enjoy and/or are interested in could work to your advantage since it is not as painful to study and perform well in a subject that you are interested in.
Relevance to tertiary studies:
If applicable, you should consider whether any of your subjects has some relevance to what you intend to study beyond the HSC, irrespective of whether they are treated as prerequisites/assumed knowledge.
Business Studies, especially the HSC course, provides a foundation of knowledge that could be useful if you intend to study a Bachelor of Business/Commerce or a similar degree. Similarly, Biology and Chemistry would be good to have if you intend to study a Bachelor of Science or a similar degree. Mathematics Advanced is a prerequisite for a number of USyd courses, which is something to keep in mind if USyd is an option.
The subject with the (potentially) least reference to university studies would be PDHPE. Because of this, you may wish to consider dropping PDHPE.
I hope this helps!
