A.I. Explanation:

First sentence: Why this is the first line? This paragraph is the first because it introduces the main topic of the text. It talks about the Ice Ages and their importance for mankind. This is a broad overview of the subject. It does not use any pronouns or definite articles that need prior context. Why other lines are not chosen? The other paragraphs are not independent. For example, Paragraph 2 starts with "The effect" which uses the definite article "the" and assumes prior knowledge. Paragraph 3 starts with "This narrows" which uses a pronoun that refers back to something not yet mentioned. Paragraph 4 starts with "One such sunken ridge" which also uses a pronoun. Paragraph 5 starts with "Another lies" which uses a pronoun that needs context.

Concluding sentence: Why this is the last line? This paragraph is the last because it gives a final example of a sunken ridge. It wraps up the discussion about the Ice Ages and their effects on land connections.

Paragraph pairs:

• Pair 1 (Paragraph 1 → Paragraph 2): Paragraph 2 connects to Paragraph 1 because it explains how the Ice Ages affect sea levels. This shows a logical order from the importance of Ice Ages to their effects.
• Pair 2 (Paragraph 2 → Paragraph 3): Paragraph 3 connects to Paragraph 2 because it explains what happens when the sea level lowers. It shows a cause and effect relationship.
• Pair 3 (Paragraph 3 → Paragraph 4): Paragraph 4 connects to Paragraph 3 because it gives an example of a sunken ridge. This follows the broader to specific strategy, moving from a general statement to a specific example.
• Pair 4 (Paragraph 4 → Paragraph 5): Paragraph 5 connects to Paragraph 4 because it introduces another example of a sunken ridge. This shows a logical order of examples.