A.I. Explanation:

First sentence: Why this is the first line? This paragraph is the first sentence because it introduces the main topic of urbanization. It gives a broad overview of what urbanization is and its importance. It does not use any specific details or references to other sentences. Why other lines are not chosen? The other paragraphs do not qualify as the first sentence. For example, Paragraph 2 starts with 'It', which is a pronoun that refers back to something else. Paragraph 3 starts with 'This shift', which also refers to a previous idea. Paragraph 4 starts with 'However', which is a conjunction and shows a contrast. Paragraph 5 starts with 'Therefore', which indicates a conclusion and cannot be the first sentence.

Concluding sentence: Why this is the last line? This paragraph is the last sentence because it wraps up the discussion. It gives a conclusion about urbanization and emphasizes the importance of managing it. The word 'Therefore' signals that this is the final thought.

Paragraph pairs:

• Pair 1 (Paragraph 1 → Paragraph 2): Paragraph 2 connects to Paragraph 1 because it gives more detail about urbanization. It explains what urbanization involves, which is the migration of people. This is a logical order from a general statement to a specific example.
• Pair 2 (Paragraph 2 → Paragraph 3): Paragraph 3 connects to Paragraph 2 because it describes the effects of the migration mentioned in Paragraph 2. The word 'This shift' refers back to the migration, showing a clear link between the two ideas.
• Pair 3 (Paragraph 3 → Paragraph 4): Paragraph 4 connects to Paragraph 3 because it presents a contrast. While Paragraph 3 talks about the positive effects of urbanization, Paragraph 4 introduces a problem that comes with rapid urbanization. The word 'However' shows this contrast.
• Pair 4 (Paragraph 4 → Paragraph 5): Paragraph 5 connects to Paragraph 4 because it offers a solution to the problem mentioned in Paragraph 4. The word 'Therefore' indicates that the following sentence is a conclusion or a response to the issues raised.