The correct answer is Martin Luther King Jr.
The Montgomery Bus Boycott started after the NAACP and Rosa Parks agreed to challenge a Montgomery law forcing black citizens to give up their seats to white citizens. After Parks was arrested for violating this law, members of the African American community and NAACP worked to organize a boycott. This refusal to ride on Montgomery public buses was made widespread thanks to speeches by people like Martin Luther King Jr. Ultimately, this boycottt was successful as the city of Montgomery changed their policy roughly one year after the boycott began.