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, which is the First World War. It gives a broad overview of the war and does not refer to any previous information. This follows the rule of Topic Sentence. Why other lines are not chosen? Paragraph 2 starts with 'Even today,' which refers to a time after the war, so it cannot be first. Paragraph 3 starts with 'Triggered by,' which needs context from the war, so it cannot be first. Paragraph 4 starts with 'Consequently,' which shows it is linked to something before it, so it cannot be first.

Concluding sentence: Why this is the last line? This paragraph is the last sentence because it wraps up the text by reflecting on the long-term effects of the war. It uses the phrase 'Even today,' which signals a conclusion about the war's impact.

Paragraph pairs:

• Pair 1 (Paragraph 1 → Paragraph 2): Paragraph 2 connects to Paragraph 1 because it gives more details about the war. The phrase 'Triggered by the assassination' shows a cause for the war, which follows the Logical Order rule.
• Pair 2 (Paragraph 2 → Paragraph 3): Paragraph 3 connects to Paragraph 2 because it shows the result of the war. The word 'Consequently' shows a cause and effect relationship, which follows the Cause and Effect Relationship rule.
• Pair 3 (Paragraph 3 → Paragraph 4): Paragraph 4 connects to Paragraph 3 because it summarizes the lasting impact of the war. The phrase 'Even today' shows that the effects are still felt, which follows the Broader to Specific Strategy.