可用来制铅笔芯的是 [ ]
A．铅
B．金刚石
C．石灰石
D．石墨
答案：D
点P在第四象限，P到x轴的距离为4，P到y轴距离为3，则点P的坐标为______．
A boy with two dogs ______when the earthquake rocked the city.
A．were sleeping
B．is asleep
C．was sleeping
D．are asleep
