Answer:
A. Mrs. White believes her dead son is knocking at the door and goes downstairs to open the door.
Step-by-step explanation:
This is the statement that best describes what happens at the climax of the story "The Monkey's Paw." The monkey's paw grants wishes, and the second wish that it granted the family was to be able to see Mr. and Mrs. White's dead son again. Therefore, the moment when Mrs. White believes her dead son to be at the door is the moment of most excitement and tension, as we wait to find out whether the son has really come back to life.