The "ghost" that Phoenix sees is a scarecrow. Option B is correct.
Phoenix was an aged and frail as well as fierce woman (she was born into slavery in the pre-Civil-War South, though the story takes place in 1940), will not allow anything in her path to stop her from achieving her end goal, which is to retrieve medicine in town for her grandson.
Since she is very old and frail, she has difficulty seeing and faces many obstacles when walking along the worn path into town. For instance, she has difficulty with seeing the scarecrow, which she initially thinks is a ghost.