Answer: A) An angel rescues the sweepers from their coffins.
Explanation: "The Chimney Sweeper" is a poem that relates the story of a child that was sold by his father into child labour after his mother died, the child was forced to be a chimney sweeper. In the given passage we can see the description of the child's (William Blake) dream, where he and other children were locked up in coffins and an angel with a bright key rescues them and set them all free.