Some guy at our school said that on the multiple choice sheet if you make a mistake in pencil, then you should cross it out rather than rub it out. I can't believe why this would be the case when you are expected to bring in an eraser and a pencil, especially for multiple choice, but could anybody shine some light on this - particularly past students.
They mark the multiple choice sheets by scanning them through a computer - the computer detects the lead on the answer, then gives you a 1 or 0 if you got it right. If the computer detects more than one circle coloured in, you automatically get a zero. If you cross out an answer, it's still coloured in, so you get a zero for colouring in another...
So, COMPLETELY ERASE an option if you want to pick another answer. They say this clearly in the exam instructions, so hopefully this person takes note of that...
On short answer, though, crossing out is perfectly fine and encouraged. (Y)