I just finished taking my AS level exams in November and have progressed to A2 level whilst waiting for my results that will come out in January next year (2024). I have doubts that I might not do well in my AS level Biology. If that turns out to be true, is it possible for me to just resit Biology AS level for that one subject whilst still progressing in A2? Or must I resit for all the other subjects that I took in AS? Is it also possible to resit AS while also taking A2 in the same exam season (May/June)?