100. 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.