A.I. Explanation:

First sentence: Why this is the first line? This paragraph is the first line because it introduces the main topic of military purpose. It does not need another sentence for context. It is a general statement about defence. Why other lines are not chosen? Paragraph 2 starts with a question, which does not stand alone. Paragraph 3 uses 'the' which assumes prior knowledge. Paragraph 4 is a question and does not provide context. Paragraph 5 uses 'but' which shows contrast and needs prior information. Paragraph 6 uses 'now' which indicates a time reference and needs context.

Concluding sentence: Why this is the last line? This paragraph is the last line because it wraps up the discussion about different eras. It provides a final example of how to destroy productive capacity in the information era, concluding the overall theme.

Paragraph pairs:

• Pair 1 (Paragraph 1 → Paragraph 2): Paragraph 2 follows Paragraph 1 because it asks a question about the topic introduced in Paragraph 1. This is a logical order as the question relates directly to the purpose of the military.
• Pair 2 (Paragraph 2 → Paragraph 3): Paragraph 3 answers the question from Paragraph 2. This shows a clear question→answer structure, linking the two paragraphs.
• Pair 3 (Paragraph 3 → Paragraph 4): Paragraph 4 gives a specific example of the idea in Paragraph 3. This follows the broader to specific strategy, where a general idea is followed by a specific case.
• Pair 4 (Paragraph 4 → Paragraph 5): Paragraph 5 contrasts with Paragraph 4 by discussing a different era. The use of 'but' shows a contrast between the agrarian and industrial eras, linking the two ideas.
• Pair 5 (Paragraph 5 → Paragraph 6): Paragraph 6 continues the discussion of different eras. The word 'now' indicates a shift to the next era, showing chronological order.