A.I. Explanation:

First sentence: Why this is the first line? This paragraph is the first sentence because it introduces the main topic of how mountains are formed. It gives a clear overview of the process of mountain building without needing other sentences for context. This follows the rule of Topic Sentence. Why other lines are not chosen? Paragraph 2 starts with "Such mountains" which refers back to the mountains mentioned in Paragraph 1, so it cannot be first. Paragraph 3 starts with "Another way" which suggests it is not the main idea but a continuation. Paragraph 4 starts with "These movements" which also refers back to earlier ideas, making it not independent.

Concluding sentence: Why this is the last line? This paragraph is the last sentence because it summarizes the effects of the movements discussed in the previous paragraphs. It wraps up the topic by showing the results of the mountain formation processes.

Paragraph pairs:

• Pair 1 (Paragraph 1 → Paragraph 2): Paragraph 2 connects to Paragraph 1 because it explains what kind of mountains are being discussed. This follows the Broader to Specific Strategy, where the first paragraph gives a general idea and the second provides a specific name for those mountains.
• Pair 2 (Paragraph 2 → Paragraph 3): Paragraph 3 connects to Paragraph 2 because it introduces another method of mountain formation. This follows the Logical Order rule, as it shows a different way mountains can form after explaining fold mountains.
• Pair 3 (Paragraph 3 → Paragraph 4): Paragraph 4 connects to Paragraph 3 because it explains the results of the movements mentioned in Paragraph 3. This follows the Cause and Effect Relationship rule, where the movements lead to the creation of flat-topped mountains and valleys.