一台很先进的计算机，可以不要操作系统，就能正常工作。

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