The correct answer is option D: School uniforms should be required because they eliminate socio-economic distinctions between students of varying backgrounds.
The grammar and overall syntax of the previous three statements is somewhat convoluted.
Option A leaves open the day that uniforms should be required until socio-economic distinctions are eliminated. An uncertain day that may never come.
Option B makes it sound like the obligation of wearing uniforms comes as a result of 'socio-economic distinctions being minimized.
Option C is phrased awkwardly although its sentences are correct.
B. Professionalism
As person with integity behaves according to the rules and standards of his or her job or profession, it is closely related to being professional. Integrity also includes having high standards of your own and behaving according to them.