What did Martin Luther King, Jr. do?

Martin Luther King, Jr. is widely recognized for his pivotal role in the civil rights movement during the 1950s and 1960s. He advocated for nonviolent resistance to racial segregation and discrimination, leading many notable campaigns and movements aimed at achieving equality for African Americans. King is best known for his leadership during events such as the Montgomery Bus Boycott and the March on Washington, where he delivered his famous "I Have a Dream" speech. His efforts helped to bring about significant legal changes, including the Civil Rights Act of 1964 and the Voting Rights Act of 1965.

The other options do not accurately reflect King's legacy or contributions. His involvement in World War II is not part of his biography; he was a civil rights leader rather than a politician, so he did not serve in the Senate or create a political party. Thus, his dedication to fighting for civil rights stands out as his most significant achievement.