A.I. Explanation:

First sentence: Why this is the first line? This paragraph is the first sentence because it introduces the main topic of climate change. It clearly states that climate change is a global issue caused by human actions. This follows the rule of Topic Sentence. Why other lines are not chosen? Paragraph 2 starts with "Many factors" which is not independent because it refers to factors without introducing the topic first. Paragraph 3 starts with "To mitigate" which is not independent because it assumes prior knowledge of climate change. Paragraph 4 starts with "The consequences" which is not independent because it uses the definite article "the" and assumes prior context.

Concluding sentence: Why this is the last line? This paragraph is the last sentence because it summarizes the effects of climate change. It wraps up the discussion by showing the serious results of climate change, following the Summary Style rule.

Paragraph pairs:

• Pair 1 (Paragraph 1 → Paragraph 2): Paragraph 2 connects to Paragraph 1 because it explains the factors that cause climate change. This follows the Logical Order rule, as it continues the discussion about climate change.
• Pair 2 (Paragraph 2 → Paragraph 3): Paragraph 3 connects to Paragraph 2 because it talks about what nations must do to help with climate change. This follows the Cause and Effect Relationship rule, as it shows the need for action based on the factors mentioned.
• Pair 3 (Paragraph 3 → Paragraph 4): Paragraph 4 connects to Paragraph 3 because it describes the results of not taking action. This follows the Cause and Effect Relationship rule, as it shows the negative outcomes of climate change.