Which of the following has an error in parallel structure

How does langston hughes use the denotative meaning of the word uniform ironically in his poem "will v-day be me day too"? a. to show that african americans faced segregation even while fighting for their country alongside americans of other races b. to show that african americans enlisted in the war hoping to gain acceptance and equality in their country c. to show that by donning the u.s. army uniform, the people of america stood united, irrespective of their race d. to show that african americans who were part of the armed forces were treated with dignity