Rechecking for the principle of the thing?

Hey, all

I got B2 in Biology and was delighted with that. The respiration question was a nightmare so couldn't believe my work had paid off and I had actually done well. For curiosity's sake I looked at my paper on Friday. Turns out I was only 1% away from a B1. However, I lost marks on a question where I know my answers were right. I actually have a Psychology degree and we did lab experiments every week, so I know exactly what a feckin' control group is and why you isolate your variables etc. Yet the examiner marked those answers as 0. I know they were right as such things were beat into us during my degree. However, my work has paid off and I've gotten into the masters I wanted to do. So I'd really only be appealing for the principle of the thing. It's really bothering me though as I know I'm right. Yet money is tight now that I'm going back to college as a mature student so it seems a bit mad to spend 40 on this. Would welcome opinions. It's bugging me.