Final answer:
The underlined text confirms a pattern of procrastination and hints at a deeper unwillingness to write, as the character consistently finds excuses to avoid starting his supposed book project.
Step-by-step explanation:
The underlined portions of the text shape a central idea of the story by highlighting the character's consistent use of excuses to avoid starting the book he intends to write. Based on the provided excerpts, the lines indicate that the character's reasons for delaying writing evolve with the seasons - from the claim about the inadequacy of gas-light to the changing preferences of writing in different seasons. The shift in the character's reasoning from optimistic postponement to outright irritation when reminded of the book suggests a pattern of procrastination and potentially a deeper reluctance or lack of intention to write. Therefore, answer C, by confirming that the husband will always have an excuse about why it is not the time to write, best captures the essence of how the underlined text contributes to the story's central theme.