Final answer:
The climax of this story is John's capture at Harper's Ferry.
Step-by-step explanation:
The climax of a story is the high point of interest and tension in the narrative. It is the turning point of the story where the conflict reaches its peak and a major event takes place. In this story, the climax is option d) John's capture at Harper's Ferry. This event represents the culmination of the main conflict and has significant consequences for the characters involved.