A GSCE exam paper has prompted fury after pupils were left baffled by what appeared to be a business studies question in a biology exam.
A question in the AQA Biology paper reportedly asked pupils to define an "independent company", prompting streams of children to complain about the exam on social media.
There were more than 100,000 tweets about the exam within hours of the paper being taken, but the exam board has denied there was any mistake.
Many took to Twitter to claim there wasn't enough biology on the exam paper.
Jack Green, 16, a pupil at South Hunsley School in North Ferriby, East Yorkshire, said pupils were "worried" about their grades as they thought the exam was very different to the syllabus they had been taught.
As well as the 'independent company' question, Jack said the exam also contained a question about 15-year-olds' favourite alcoholic drink.
"It was like 'what is a teenage boy's favourite drink?' - I don't have a clue what that had to do with biology," he said.
Jack rang the board to complain about the paper.
"They were making out like it was a mistake, the guy on the phone said that something went wrong.
"It's stuff that we've never been taught and that's not the teachers' fault, it's the exam board's fault because they didn't tell the teachers to teach us it.
"I'm hoping that they'll either let people through with their target grade, which is something they've done before, or recall the papers and send out a new one.
"It's my first GCSE exam that I've done and it's like 'are all GCSE exams going to be stuff that I haven't been taught'?"
He said that many other pupils in the exam hall appeared to be struggling.
"A lot of people you could see were stressing out. Every time I looked up to look at the clock there was someone there tapping their pen on the desk, agitated."
"Everyone's a bit worried because this biology exam has such a high weighting for the total grades so it's really affecting what the overall grade will be."
An AQA spokeswoman said that the 'independent company' question was one of several on the subject of drug trails, and that the underage drinking question was in a section on alcohol abuse. The exam board said that both questions were included on the syllabus.
She said: "Exams aren't meant to be easy and students are obviously going to tweet about that, but there was nothing wrong with this paper.
"We wish everyone the best of luck with the rest of their exams."