饮料用水首先必须符合（）。
参考答案：生活饮用水水质标准（GB5749-1985）
Arriving home，the boy told his parents about all the________which occurred in his dormitory.
A．occasions
B．incidents
C．matters
D．accidents
求点P(1，1，1)到旋转抛物面S：z=x2+y2在点(1，1，2)处的切平面的距离．
