用in,on,under或behind填空
I have a nice and clean room .There is a small desk 1.____ the room .My clock is 2.____ the desk .The soccer ball is 3.____ the bed .My schoolbag is 4.____ the door of the room .My pen and eraser are not 5.____ the pencil box .The pencil box is not 6.____ the schoolbag .It's 7.____ the desk .