Final answer:
A 'Terry stop' is the correct answer to the question about an investigatory stop that allows a pat-down for weapons based on reasonable suspicion. It is distinct from consent searches, searches under exigent circumstances, and the plain view doctrine.
Step-by-step explanation:
An investigatory stop that includes a pat-down for weapons when an officer has reasonable suspicion that a suspect is armed is referred to as a Terry stop. This term comes from the landmark case Terry v. Ohio, where the Supreme Court held that police may stop and frisk a suspect for weapons without violating the Fourth Amendment, provided they have reasonable suspicion that the person is involved in criminal activity and is armed and dangerous.
This principle is distinct from a consent search, where a person voluntarily allows the police to conduct a search without any coercion or suspicion. It also differs from searches under exigent circumstances, which are searches conducted without a warrant due to urgent situations, and the plain view doctrine, which allows officers to seize evidence without a warrant if it is clearly visible.