Which of the following is an example of the use of boycotts to achieve policy reform?

pushing for the passage of legislation that would prohibit discrimination against Black people in the workplace and in schools

bringing a lawsuit against a university for discriminatory admissions practices that put Black students at a disadvantage

volunteers holding voter registration drives to increase voter registration and turnout among Black voters in the next election

African Americans refusing to use the public transit system in Montgomery, Alabama that discriminated against passengers