A.I. Explanation:

First sentence: Why this is the first line? This paragraph is the first sentence because it gives a clear topic. It talks about deaths caused by sea level rise. This is an introduction to the main idea. It does not need another sentence to understand it. It does not use words like 'however' or 'moreover' that need more context. Why other lines are not chosen? Paragraph 2 starts with 'This number' which needs context from the first sentence. Paragraph 3 starts with 'If sea level rises' which is a conditional phrase and needs more information. Paragraph 4 starts with 'If sea level rises' too, which also needs context. All these sentences cannot stand alone.

Concluding sentence: Why this is the last line? This paragraph is the last sentence because it gives the final detail about deaths from sea level rise. It shows the worst case if sea level rises 1 meter. It wraps up the topic by showing the highest number of deaths.

Paragraph pairs:

• Pair 1 (Paragraph 1 → Paragraph 2): Paragraph 2 connects to Paragraph 1 because it uses the word 'This number.' This shows that it talks about the deaths mentioned in the first paragraph. This is a clear link.
• Pair 2 (Paragraph 2 → Paragraph 3): Paragraph 3 connects to Paragraph 2 because it starts with 'According to the research.' This shows that it continues the idea from the second paragraph. It gives more details about the research.
• Pair 3 (Paragraph 3 → Paragraph 4): Paragraph 4 connects to Paragraph 3 because it talks about another level of sea rise. It continues the topic of deaths due to sea level rise. This shows a logical order.