Comment if you know the correct answer

What made slavery legal was D. the Bill of Rights, Because amendment 13 officially abolished slavery in the United States and continues to this day.

So D. is your anwser.

Hope this helps. :) 

United states v.  nixon, 418  u.s.  683 (1974),  was  a landmark  united states supreme court case  that resulted in a unanimous  decision  against president richard  nixon, ordering him to deliver tape recordings  and  other subpoenaed materials to a  federal  district  court.

That is true , instead try to have a sit down talk with them