A.I. Explanation:

First sentence: Why this is the first line? This paragraph is the first sentence because it introduces the main topic of the text, which is the Industrial Revolution. It gives a broad overview of this important event without going into details. This follows the rule of Topic Sentence. Why other lines are not chosen? The other paragraphs are not chosen because they do not stand alone. For example, Paragraph 2 starts with 'It', which is a pronoun and needs context. Paragraph 3 has a specific time reference and is not general. Paragraph 4 uses 'This period', which also needs prior context.

Concluding sentence: Why this is the last line? This paragraph is the last sentence because it summarizes the key points of the text. It gives specific examples of the developments during the Industrial Revolution, wrapping up the discussion. This follows the Summary Style rule.

Paragraph pairs:

• Pair 1 (Paragraph 1 → Paragraph 2): Paragraph 2 connects to Paragraph 1 because it continues the topic of the Industrial Revolution. The phrase 'It started' refers back to the Industrial Revolution, showing a logical flow of ideas. This follows the Noun Pronoun Rule.
• Pair 2 (Paragraph 2 → Paragraph 3): Paragraph 3 connects to Paragraph 2 because it explains what happened during the Industrial Revolution. The phrase 'This period' refers back to the Industrial Revolution, showing a clear connection. This follows the Noun Pronoun Rule.
• Pair 3 (Paragraph 3 → Paragraph 4): Paragraph 4 connects to Paragraph 3 because it gives specific examples of the developments mentioned in Paragraph 3. The phrase 'Significant developments' shows a logical order from general to specific, following the Broader to Specific Strategy.