Multi-choice answer sheets should be answered in pencil as these are marked by a computer system. If you answer in pen you can't erase your answer if you want to change it and the system will not mark the question if there is more than one mark on the answer paper grid.
The instructions given to candidates for written answers state: "Write in ink on both sides of the paper. Marks are deducted for writing which is not easily legible. (pencils may be used for diagrams, graphs or for completing multi-choice answer sheet to be computer marked.)"
It is highly recommended that you use pen for your answers (unless otherwise stated) as this is permanent on paper in comparison to pencil. However a pencil written answer will still be marked.