Answer:
c.local police collaborated with the white mobs that attacked buses.
Step-by-step explanation:
Freedom Riders were groups of white and African American civil rights who participated in Freedom Rides in 1961 with the aim to desegregate interstate transportation, including highways, bus stops, and train terminals and to test the Supreme Court's ruling in Boynton v. Virginia (1960), which declared segregation in interstate bus and rail stations unconstitutional.
During the Freedom Rider was met with an incident where local police collaborated with the white mobs that attacked buses in Birmingham, Alabama, where the police chief saw the Freedom Ride as a challenge to his authority in the city.