Answer:
D). Struggle with painful physical symptoms .
Step-by-step explanation:
In the context of the novel 'Three Men in a Boat,' the author facilitates the plot by displaying 'narrator's scuffle with aching physical symptoms.' These physical challenges during their journey compel the characters to take unexpected decisions and moves the story forward, keep the readers' interest intact, and the consequences of these actions lead the story towards its climax. Thus, option D is the correct answer.