 Less-used types of bonus questions include list bonuses, which require players to give their answers from a requested list, and "30-20-10" bonuses, which give a number of discrete clues for a single answer in order of decreasing difficulty, with more points being awarded for giving the correct answer on an earlier clue.The 30-20-10 bonus was officially banned from ACF in 2008 and NAQT in 2009.Several variations on the game of quiz bowl exist that affect question structure and content, rules of play, and round format.