点燃蜡烛的过程中( )
A:只发生化学变化
B:只发生物理变化
C:没有发生物理变化
D:既有物理变化又有化学变化
His parents were worried that he______ too much time chatting on line.
点P关于x轴对称点P1的坐标是(4,﹣8),则P点关于原点的对称点P2的坐标是( )