What important question about the legal status of black people remained unanswered after the passage of the 13th amendment?

Black codes were restrictive laws designed to limit the freedom of African Americans and ensure their availability as a cheap labor force after slavery was abolished during the Civil War. Though the Union victory had given some 4 million slaves their freedom, the question of freed blacks’ status in the postwar South was still very much unresolved. Under black codes, many states required blacks to sign yearly labor contracts; if they refused, they risked being arrested, fined and forced into unpaid labor. Outrage over black codes helped undermine support for President Andrew Johnson and the Republican Party.

i would go with the last one

the answer is d. selective incorporation. (apex)