A:see
B:door
C:chair
煮沸的肉汤放置不久就会腐败变质,原因是 ( )
选择搭配合理的句子
——Do you think Peter is free today?
——__________. He is really busy preparing(准备) for the coming test these days.
从六边形的一个顶点出发,可以画出m条对角线,它们将六边形分成n个三角形.则m、n的值分别为( )