put the sausage on top of the tomato paste.这句.顺便讲讲on top of the tomato paste是什么意思还有一个是 on top of the green pepper. on top of 什么意思啊???bake the pizza in a hot oven for 20 minutes.还有这句.很少简单.课本知识而已只是我不懂啊.