You are attempting to administer CPR to a victim. When you blow into his mouth it is apparent that no air is getting into the lungs. What should you do?

A
Blow harder to force the air past the tongue.
B
Raise the victim's head higher than his feet.
C
Press on the victim's lungs so that air pressure will blow out any obstruction.
D
Re-tip the head and try again.
E