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. It gives a broad overview of the origins of the modern Welfare State in Britain. This follows the rule of Topic Sentence. It does not refer to any previous information, so it stands alone. Why other lines are not chosen? The other paragraphs are not chosen because they do not meet the criteria for being independent. For example, Paragraph 2 starts with 'That year,' which refers back to a specific time and is not independent. Paragraph 3 starts with 'They,' which is a pronoun that refers back to the Liberal party, so it is not independent. Paragraph 4 starts with 'But,' which is a conjunction and does not stand alone.

Concluding sentence: Why this is the last line? This paragraph is the last sentence because it wraps up the discussion about the Liberal party's actions. It provides a conclusion to the ideas presented in the previous paragraphs. This follows the Conclusive Words rule, as it gives a final thought on the topic.

Paragraph pairs:

• Pair 1 (Paragraph 1 → Paragraph 2): Paragraph 2 connects with Paragraph 1 because it gives a specific event that relates to the origins mentioned in Paragraph 1. This follows the Broader to Specific Strategy.
• Pair 2 (Paragraph 2 → Paragraph 3): Paragraph 3 connects with Paragraph 2 because it explains what happened after the victory of the Liberal party. This follows the Logical Order rule, as it shows the next step in the narrative.
• Pair 3 (Paragraph 3 → Paragraph 4): Paragraph 4 connects with Paragraph 3 because it gives a contrast to the introduction of welfare reforms. This follows the Contrast rule, as it shows a different side of the situation.