The correct answer is:
A. They refused to ride segregated buses.
African Americans in Montgomery, Alabama, played a significant role in the civil rights movement by initiating the Montgomery Bus Boycott. This boycott was a pivotal moment in the struggle against racial segregation, sparked by the arrest of Rosa Parks for refusing to give up her seat to a white person on a segregated bus. The African American community in Montgomery united to boycott the city's bus system, demanding an end to segregated seating. This nonviolent protest ultimately led to a Supreme Court ruling that declared segregated buses unconstitutional, marking a significant victory in the civil rights movement.