A.I. Explanation:

First sentence: Why this is the first line? This paragraph is the first sentence because it introduces the main topic of de-industrialisation and its effects. It gives a broad overview of the issue without needing prior context. This follows the rule of Topic Sentence. Why other lines are not choosen? Other paragraphs are not chosen because they do not stand alone. For example, Paragraph 2 starts with 'But', which is a conjunction. Paragraph 3 uses 'As', which also shows it is not independent. Paragraph 4 uses 'Policy should', which assumes prior knowledge. Paragraph 5 uses 'Protection', which is not general. Therefore, they do not qualify as the first sentence.

Concluding sentence: Why this is the last line? This paragraph is the last sentence because it wraps up the discussion by giving a clear conclusion about the ineffectiveness of protection and subsidies. It summarizes the main points made earlier and reflects the overarching theme of the text.

Paragraph pairs:

• Pair 1 (Paragraph 1 → Paragraph 2): Paragraph 2 connects to Paragraph 1 because it shows a contrast. The word 'But' is a connector that indicates a different view on how to solve the problems mentioned in Paragraph 1. This follows the Contrast rule.
• Pair 2 (Paragraph 2 → Paragraph 3): Paragraph 3 connects to Paragraph 2 by explaining the reason why subsidies or trade barriers are not effective. The word 'As' shows a cause and effect relationship. This follows the Cause and Effect Relationship rule.
• Pair 3 (Paragraph 3 → Paragraph 4): Paragraph 4 connects to Paragraph 3 because it gives a solution to the problem of shrinking manufacturing. The phrase 'Policy should therefore focus' shows a logical order from the problem to the solution. This follows the Logical Order rule.
• Pair 4 (Paragraph 4 → Paragraph 5): Paragraph 5 connects to Paragraph 4 by showing a contrast to the policy suggested. The phrase 'Protection and subsidies push just the wrong way' indicates that these actions are not helpful. This follows the Contrast rule.