点P（-2，3）关于原点O对称的点P′的坐标是______．

When starting CPR on a drowning victim，you should（）.

A.start chest compressions before the victim is removed from the water

B.drain water from the lungs before ventilating

C.begin mouth-to-mouth ventilations as soon as possible

D.do not tilt the head back since it may cause vomiting