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 uses the rule of Topic Sentence. It gives a broad overview of how technology has changed fitness without going into details. Why other lines are not chosen? The other paragraphs are not independent. For example, Paragraph 2 starts with 'For example,' which is a conjunction. Paragraph 3 starts with 'They,' which is a pronoun that refers back to something else. Paragraph 4 starts with 'However,' which is also a conjunction. These words show that they need more context to make sense.

Concluding sentence: Why this is the last line? This paragraph is the last sentence because it wraps up the discussion by showing a problem with technology in fitness. It uses conclusive words like 'however' to signal that it is giving a final thought.

Paragraph pairs:

• Pair 1 (Paragraph 1 → Paragraph 2): Paragraph 2 connects with Paragraph 1 because it gives a specific example of how technology has changed fitness. This follows the Broader to Specific Strategy.
• Pair 2 (Paragraph 2 → Paragraph 3): Paragraph 3 connects with Paragraph 2 because it explains more benefits of fitness apps and wearable tech. This shows a Logical Order of ideas.
• Pair 3 (Paragraph 3 → Paragraph 4): Paragraph 4 connects with Paragraph 3 because it presents a contrast to the benefits mentioned in Paragraph 3. This uses the Contrast rule.