In Fugard’s "Master Harold"…and the Boys, the falling action best describes the part of the play in which Hally spits in Sam’s face. Option B is correct.
Falling action takes place following the climax, when the primary problem of the story resolves. It is one of the elements of the plot of the story, in addition to the exposition, rising action, climax, and resolution. Falling action wraps up the narrative, resolves its loose ends, and leads toward the closure.