Final answer:
The most appropriate sentence to end Paragraph 3 is 'When the backyard has been secured, he comes back inside and settles down for a solid nap.' as it maintains the story's consistent and readable style for a middle school audience.
Step-by-step explanation:
When adding a sentence that complements the existing paragraphs in meaning and style, it is important to maintain both the consistency of the narrative and the readability for the audience's level of understanding. In this context, with the description of Pudge's routine and personality, the sentence that fits best stylistically and maintains the story's flow would be the following:
When the backyard has been secured, he comes back inside and settles down for a solid nap.
This choice reflects the casual yet descriptive storytelling technique used throughout the piece, effectively conveying Pudge's actions without altering the established tone or complexity.