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 talks about how we connected computers in the past. This is a broad overview of the topic. It does not use any pronouns or definite articles that need prior context. Why other lines are not chosen? The other paragraphs are not chosen because they do not meet the criteria for being independent. For example, Paragraph 2 starts with 'In the last few years,' which is a time clue and shows it is not independent. Paragraph 3 starts with 'But,' which is a conjunction. Paragraph 4 starts with 'What,' which is a question and does not stand alone.

Concluding sentence: Why this is the last line? This paragraph is the last sentence because it wraps up the discussion. It asks important questions about the topic. This shows that the text is coming to an end.

Paragraph pairs:

• Pair 1 (Paragraph 1 → Paragraph 2): Paragraph 2 connects with Paragraph 1 because it continues the topic of connection. The phrase 'In the last few years' shows a logical order of time, moving from the past to the present.
• Pair 2 (Paragraph 2 → Paragraph 3): Paragraph 3 connects with Paragraph 2 because it asks a question about the meaning of the previous information. The word 'But' shows a contrast and leads to a new thought.
• Pair 3 (Paragraph 3 → Paragraph 4): Paragraph 4 connects with Paragraph 3 because it continues the question from the previous paragraph. It asks about possibilities and threats, which are related to the meaning discussed.