Which civil rights figure advocated for farm workers and collaborated closely with Cesar Chavez?

Dolores Huerta was a pivotal figure in advocating for the rights of farm workers and played a critical role alongside Cesar Chavez in the United Farm Workers (UFW) movement. She co-founded the UFW and helped organize strikes, boycotts, and various forms of activism aimed at improving the working conditions and wages of agricultural laborers, particularly in California. Huerta's work not only focused on labor rights but also emphasized broader social justice issues, including immigration and women's rights. Her leadership and advocacy efforts were integral to the success of the farm workers' movement in the 1960s and 1970s.

In contrast, Martin Luther King Jr. was primarily focused on civil rights for African Americans, rather than farm workers. Eleanor Roosevelt was known for her humanitarian efforts and advocacy for civil rights, but her work did not specifically target the rights of farm workers as a central focus. Betty Friedan was a leading figure in the feminist movement, advocating for women's rights, but her activism did not intersect significantly with labor rights in the agricultural sector. Therefore, Dolores Huerta stands out as the correct choice due to her direct involvement and impact in advocating for farm workers alongside Cesar Chavez.