A.I. Explanation:

First sentence: Why this is the first line? This paragraph is the first sentence because it introduces the main topic of caffeine and its effects. It gives a broad overview of what caffeine is and what it does. It does not need other sentences for context. Why other lines are not chosen? Paragraph 2 starts with "This is because" which is a pronoun that needs prior context. Paragraph 3 starts with "One small study" which is specific and does not introduce the topic. Paragraph 4 starts with "Another study" which also needs prior context.

Concluding sentence: Why this is the last line? This paragraph is the last sentence because it wraps up the discussion about caffeine. It gives a final example of how caffeine helps with performance and energy. It summarizes the main points made in the earlier paragraphs.

Paragraph pairs:

• Pair 1 (Paragraph 1 → Paragraph 2): Paragraph 2 connects to Paragraph 1 because it explains how caffeine works in the body. This follows the Broader to Specific Strategy. The first paragraph gives a general idea about caffeine, and the second paragraph gives specific details about its effects.
• Pair 2 (Paragraph 2 → Paragraph 3): Paragraph 3 connects to Paragraph 2 because it provides evidence for the claims made in the second paragraph. This follows the Logical Order strategy. The second paragraph explains how caffeine works, and the third paragraph shows a study that supports this.
• Pair 3 (Paragraph 3 → Paragraph 4): Paragraph 4 connects to Paragraph 3 because it gives more examples of studies about caffeine. This follows the Same Theme strategy. Both paragraphs talk about studies that show how caffeine helps with fatigue.