Need Help??!?!I'm in trouble for some others' mistakes?

Some guys have taken my CAD printouts in a CAD exam and submitted it as theirs..Now the examiners are reducing my marks coz they took printouts from me.!!! I'll not pas the course if i don't get marks in this exam.I knew other guys took printouts from me but i could not help.Now how do i Plead my case and claim my marks...plz guys.. suggest ideas :-(