To determine which sentence best supports the main idea and the author’s motivating factors, we need to consider the central theme and the motivations expressed in the excerpt.
Based on the options provided, the sentence that most clearly reflects the author's desire to stay connected with family and share experiences through storytelling is:
C. "For the remainder of my visit, and during subsequent visits, I told her, and when he was old enough, my grandson, of the world around us and how we hoped to, some day, live together on Planet Earth."
This sentence encapsulates the author's commitment to storytelling as a means of connection and expresses a hope for a shared future with family, which aligns well with the common motivating factors of maintaining relationships and fostering a sense of togetherness despite physical distance.