♪music resumes♪ music stops ♪music resumes♪ [announcer] purina pro plan's bioavailable formulas deliver optimal nutrient absorption. [whistle] purina pro plan. nutrition that performs. welcome back melissa harris-perry is in selma, alabama this morning and we'll be checking in with her in a few moments as we continue a special edition marking the anniversary of the march in selma. it became known as bloody sunday. the national attention given to the shear brutality of that day helped to usher into law the