What is the first thing to do for someone who appears to be choking?
a. call 911.
b. perform abdominal compressions (the heimlich maneuver).
c. ask the person whether he or she is choking.
d. hit the person between the shoulder blades.

Active immunity refers to: a. the defenses people are born with. b. temporary immunity granted from another source. c. immunity gained through immunization and exposure to diseases. d. natural immunities that protect humans from other animal diseases