Many, if not most, topics of study can be taught cooperatively but that does not mean that every topic should be. Any teaching method can be overused and lose its appeal as it becomes routine. So as teachers vary the delivery of instruction, they should choose carefully the activities they use with cooperative learning. Some tasks are "naturals" for cooperative learning: activities that are easily broken into parts that can be assigned to the individuals in the group or topics on which there is likely to be a wide diversity of opinion. It is wise to restrict cooperative lessons to those that fit comfortably into a division of labor format because "forcing" a topic into a cooperative structure rarely works. Delivery of instruction with cooperative learning often takes more time than traditional approaches. If time blocks are short or if the lesson needs to be rushed, cooperative learning should be used only for small parts of the lesson, if at all. Even though cooperative activities will be interspersed with whole-group instruction, ability groups, competition and individualistic work, it is handy to have the room set up for cooperation (desks in groups of four are a common arrangement.) All of the other forms of instruction can be accommodated in such an arrangement and, then, when a cooperative opportunity presents itself, it is not necessary to rearrange the room.