First sentence: Why this is the first line? This paragraph is the first sentence because it introduces Ronald Amundsen and his important achievement. It does not need other sentences for context. It gives a broad overview of his accomplishment. Why other lines are not chosen? Paragraph 2 starts with 'But' which is a conjunction, so it cannot be first. Paragraph 3 uses 'In a well-planned dash' which needs context. Paragraph 4 mentions 'In 1926' which is a specific time and needs prior information. Paragraph 5 uses 'Two years later' which also needs context.

Concluding sentence: Why this is the last line? This paragraph is the last sentence because it wraps up Amundsen's story. It gives a final event in his life and reflects on his journey.

Paragraph pairs:

• Pair 1 (Paragraph 1 → Paragraph 2): Paragraph 2 connects to Paragraph 1 because it uses 'But' as a connector. This shows a change in direction from sailing north to sailing south.
• Pair 2 (Paragraph 2 → Paragraph 3): Paragraph 3 follows Paragraph 2 logically because it explains what happened after he turned south. It shows the next important event in his journey.
• Pair 3 (Paragraph 3 → Paragraph 4): Paragraph 4 connects to Paragraph 3 because it continues to talk about Amundsen's achievements. It shows another important event in his life after reaching the South Pole.
• Pair 4 (Paragraph 4 → Paragraph 5): Paragraph 5 follows Paragraph 4 because it talks about what happened after Amundsen's flight over the North Pole. It shows the next event in his story.