A.I. Explanation:

First sentence: Why this is the first line? This paragraph is the first line because it introduces the main topic of language and its purpose. It is a general statement that does not need another sentence for context. It does not start with a conjunction or use pronouns. It sets the stage for the discussion about language. Why other lines are not chosen? Paragraph 2 starts with 'However,' which is a conjunction. Paragraph 3 uses 'This,' which is a pronoun that refers to something earlier. Paragraph 4 also starts with 'However,' making it not independent.

Concluding sentence: Why this is the last line? This paragraph is the last line because it wraps up the discussion about language. It shows a problem that affects language diversity. It concludes the ideas presented in the earlier paragraphs.

Paragraph pairs:

• Pair 1 (Paragraph 1 → Paragraph 2): This pair connects because the second paragraph continues the idea of language. It shows how language changed over time as societies grew. This is a logical order of ideas.
• Pair 2 (Paragraph 2 → Paragraph 3): This pair connects because the third paragraph explains why languages diversified. It gives reasons for the changes mentioned in the second paragraph. This shows a clear flow of ideas.
• Pair 3 (Paragraph 3 → Paragraph 4): This pair connects because the fourth paragraph introduces a new idea about globalization. It shows a contrast to the previous discussion about language diversity. This is a logical order of ideas.