A.I. Explanation:

First sentence: Why this is the first line? This paragraph is the first line because it introduces the main topic. It talks about the impact of immigrants on the welfare state. 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? Paragraph 2 starts with "It is also..." which uses a pronoun and does not stand alone. Paragraph 3 starts with "Inevitably..." which is a transitional word. Paragraph 4 starts with "But..." which is also a conjunction. All these reasons make them not independent.

Concluding sentence: Why this is the last line? This paragraph is the last line because it wraps up the discussion. It shows that the issues are not new and gives a broader view of the topic. It reflects on the main theme of the text.

Paragraph pairs:

• Pair 1 (Paragraph 1 → Paragraph 2): This pair connects because Paragraph 2 gives more detail about the discussions mentioned in Paragraph 1. It uses the connector "also" to show that the theme is present in the press.
• Pair 2 (Paragraph 2 → Paragraph 3): This pair connects because Paragraph 3 explains what the discussions in Paragraph 2 are about. The word "inevitably" shows that it is a natural follow-up to the previous idea.
• Pair 3 (Paragraph 3 → Paragraph 4): This pair connects because Paragraph 4 contrasts with Paragraph 3. It shows that while there are present-day dilemmas, the issues have deeper historical roots. The word "but" indicates this contrast.