What's the easiest A level to do in ONE year?

Hi, I'm taking a gap year 2019-2020 due to an operation right at the start of when the uni course would begin so and I would miss the first 3 months so there's no point in starting.

However, I NEED to do something academically because I will get lazy academically if I don't. I will be working and so I will be doing this independently rather than going through the sixth form.

I am currently taking history (predicted C), English Literature (predicted B-), Biology (predicted an E- partly due to having a biology teacher who failed herself and is a complete idiot tbh) and I got an A in my EPQ.

I have an unconditional offer to study accounting and finance so I was thinking maybe accounting - and possibly reteaching myself biology and doing a resit without the practical element (which I've failed anyway due to being in hospital for so long).

Any thoughts on what I should do?