A.I. Explanation:

First sentence: Why this is the first line? This paragraph is the first line because it introduces the main topic of Frost's first publication. It does not refer to any previous information and sets the stage for the rest of the text. It uses an introductory nature and gives a broad overview of an important event in Frost's life. Why other lines are not chosen? The other paragraphs are not chosen because they do not stand alone as independent sentences. For example, Paragraph 2 starts with 'Over the next eight years,' which indicates a time frame and assumes prior context. Paragraph 3 starts with 'During this time,' which also refers back to earlier information. Paragraph 4 begins with 'But in 1912,' which suggests a contrast and requires knowledge of previous events.

Concluding sentence: Why this is the last line? This paragraph is the last line because it concludes the story of Frost's struggles and successes. It wraps up the narrative by showing how he overcame challenges and found success in England, reflecting the overarching theme of his journey.

Paragraph pairs:

• Pair 1 (Paragraph 1 → Paragraph 2): Paragraph 2 connects with Paragraph 1 because it continues the story of Frost's publishing journey. The word 'however' shows a contrast to the success of his first publication, indicating that despite this success, he faced challenges in the following years.
• Pair 2 (Paragraph 2 → Paragraph 3): Paragraph 3 connects with Paragraph 2 because it provides background information about Frost's life during the eight years mentioned. It shows what he was doing while trying to publish more poems, linking the two ideas logically.
• Pair 3 (Paragraph 3 → Paragraph 4): Paragraph 4 connects with Paragraph 3 because it explains a turning point in Frost's life. The word 'But' indicates a shift from his activities in America to his decision to move to England, showing a cause and effect relationship.