Stopping Travelers in Vehicles at a Fixed Checkpoint for Brief

Stopping travelers in vehicles at a fixed checkpoint for brief questioning about their citizenship and immigration status:

A) violates the Fourth Amendment search and seizure requirements.
B) is not considered a seizure under the Fourth Amendment.
C) is considered a seizure under the Fourth Amendment but has been held to be constitutional.
D) is considered a seizure only if officials detain the travelers for a significant amount of time.