A.I. Explanation:

First sentence: Why this is the first line? This paragraph is the first sentence because it introduces the main topic of military defence. It gives a broad overview of what the military does without going into details. This follows the rule of Topic Sentence. Why other lines are not chosen? Paragraph 2 starts with 'How do you do battle...' which is a question and does not stand alone. Paragraph 3 starts with 'The idea is...' which refers back to a previous idea. Paragraph 4 starts with 'So in the agrarian era...' which assumes prior knowledge. Paragraph 5 starts with 'But in the industrial era...' which indicates a contrast and cannot stand alone. Paragraph 6 starts with 'Now in the information era...' which also assumes prior context.

Concluding sentence: Why this is the last line? This paragraph is the last sentence because it wraps up the discussion about different eras. It shows how the topic has changed over time. This follows the Conclusive Words rule.

Paragraph pairs:

• Pair 1 (Paragraph 1 → Paragraph 2): Paragraph 2 connects with Paragraph 1 because it asks a question about the topic introduced in Paragraph 1. This follows the Question→Answer Structure rule.
• Pair 2 (Paragraph 2 → Paragraph 3): Paragraph 3 connects with Paragraph 2 because it answers the question posed in Paragraph 2. This follows the Question→Answer Structure rule.
• Pair 3 (Paragraph 3 → Paragraph 4): Paragraph 4 connects with Paragraph 3 because it gives a specific example of how to destroy the enemy’s productive capacity in the agrarian era. This follows the Broader to Specific Strategy rule.
• Pair 4 (Paragraph 4 → Paragraph 5): Paragraph 5 connects with Paragraph 4 because it contrasts the agrarian era with the industrial era. This follows the Contrast rule.
• Pair 5 (Paragraph 5 → Paragraph 6): Paragraph 6 connects with Paragraph 5 because it continues the discussion of different eras and how to destroy productive capacity. This follows the Logical Order rule.