A.I. Explanation:

First sentence: Why this is the first line? This paragraph is the first sentence because it introduces the main topic of training sessions and their importance in fitness. It gives a broad overview of what the text will discuss. This follows the rule of Topic Sentence. Why other lines are not choosen? The other paragraphs are not chosen because they do not stand alone as the first sentence. For example, Paragraph 2 starts with "The body needs..." which uses a definite article and refers to a specific idea. Paragraph 3 starts with "It is essential..." which also does not introduce a new topic. Paragraph 4 starts with "To avoid such health risks..." which assumes prior knowledge. Paragraph 5 starts with "This specificity..." which refers back to a previous idea.

Concluding sentence: Why this is the last line? This paragraph is the last sentence because it wraps up the main ideas of the text. It summarizes the importance of specificity in training and how it helps individuals. This follows the Summary Style rule.

Paragraph pairs:

• Pair 1 (Paragraph 1 → Paragraph 2): Paragraph 2 connects with Paragraph 1 because it continues the discussion about training. The first paragraph talks about principles of training, and the second paragraph explains one of those principles, which is overload. This follows the Logical Order rule.
• Pair 2 (Paragraph 2 → Paragraph 3): Paragraph 3 connects with Paragraph 2 because it explains how to apply the overload principle. The second paragraph talks about the need for overload, and the third paragraph gives advice on how to do it safely. This follows the Cause and Effect Relationship rule.
• Pair 3 (Paragraph 3 → Paragraph 4): Paragraph 4 connects with Paragraph 3 because it addresses the health risks mentioned in the third paragraph. It explains what trainers should do to avoid those risks. This follows the Logical Order rule.
• Pair 4 (Paragraph 4 → Paragraph 5): Paragraph 5 connects with Paragraph 4 because it explains the importance of specificity in training. The fourth paragraph talks about ensuring a training plan is specific, and the fifth paragraph explains how this helps maximize performance. This follows the Broader to Specific Strategy.