Question

During the last half of the Civil War, many African Americans on the Sea Islands of South Carolina and Georgia

Answer 1

For the answer to the question above, during the American Civil War, the Union Navy and the Union Army soon occupied the islands. The white planter families had fled to other locations on the mainland, sometimes leaving behind their slaves. The slaves largely ran their own lives during this period.
So the answer is C. were freed, due to the islands' occupation by Union forces.