Do you think they would give me 0 or would they be able to make an exception?
'would they make an exception' is irrelevant because they scan the paper and it will look like a blank piece of paper, maybe with very light writing, but too light to be legible. So they simply won't be able to read it and therefore can't mark it.
relax he's trolling no one is stupid enough to write with a highlighter. Even so he/she claims they didnt know they had an exam yet happened to have a highlighter with them...
Do you think they would give me 0 or would they be able to make an exception?
as I'm sure others have said, the processing centre will realise when scanning it in and they will send it out to be marked personally instead. Try not to worry. it's not that bad my English teacher told me that one time he saw a whole English paper written in Mandarin and they still had to try and mark it.