Question

when did dred scott sue for freedom for himself and his family? once he was back in the south after his enslaver died when he got to illinois

Explanation:

Dred Scott sued for freedom after his enslaver (John Emerson) died. The legal action was taken as a path to seek freedom, leveraging the situation of the enslaver's death to attempt to gain his and his family's liberty through the courts. The other options: returning to the South wouldn't prompt a freedom suit, and being in Illinois (a free state) initially was part of his journey but the suit was filed after the enslaver's death.

Answer:

B. after his enslaver died