I'd take an extra year if it's free.
If it's not free, then you'll have to see if can easily afford it.
If you can't easily afford it then I'd resit all of them next year.
Otherwise you will get overlooked in the application process when they see the AS Levels.
Personally, I would study Biology to A2 and drop Classical Civilisation instead as Biology is considered a hard Science. Consequently, unis will be drooling over you if you get a good grade.
However, I am not forcing you to do anything.
Remember don't give up and to fail to prepare is to prepare to fail.
Now a joke to make things more interesting:
-What's in the middle of Paris?
"da dum chu"!
Easiest thing to do is retake with only 3 AS subjects (preferably the ones you already have experience in - the CDE subjects). But if you feel like you can handle the pressures of carrying on to A2 with AS level resits then go ahead.
Hi, I'm in a similar situation to you. I studies history, maths, economics and chemistry. I was predicted AABC and got ADEE respectively and I am very disappointed. I'm hoping to drop chemistry and carry on with the other three. I'm just praying my teachers allow me to resit some modules of AS whilst studying for A2. I think it all depend on what you want to achieve out of A level and what u want to do after. I'd recommend speaking to your teachers or careers advisor about your aims. Good luck!!!