Officer Goldman Responds to a Call of an Active Shooter

Officer Goldman responds to a call of an active shooter during a home invasion at a local residence.Officer Goldman arrives on the scene and quickly surveys the residence.He and his partner immediately see the suspect,who is holding a semiautomatic rifle.They command the suspect to drop his weapon and the suspect complies. Outside the home,Officer Goldman pats down the suspect.He is allowed to do this without a warrant because of

A) search incident to a lawful arrest.
B) consent.
C) exigent circumstances.
D) the exclusionary rule.