A.I. Explanation:

First sentence: Why this is the first line? This paragraph is the first because it introduces the main topic of technology and communication. It does not need another sentence for context. It gives a broad overview of the topic. Why other lines are not chosen? Paragraph 2 starts with "In the past," which refers to a time before the current topic. Paragraph 3 uses "This" which refers back to something not yet mentioned. Paragraph 4 uses "This" as well, which also needs prior context.

Concluding sentence: Why this is the last line? This paragraph is the last because it wraps up the main idea. It shows the overall effect of the changes in communication.

Paragraph pairs:

• Pair 1 (Paragraph 1 → Paragraph 2): Paragraph 2 connects with Paragraph 1 because it continues the idea of technology. The word "Nowadays" shows a logical order from the advances in technology to how we use it today.
• Pair 2 (Paragraph 2 → Paragraph 3): Paragraph 3 connects with Paragraph 2 because it contrasts the current way of communication with the past. The phrase "In the past" shows a clear contrast.
• Pair 3 (Paragraph 3 → Paragraph 4): Paragraph 4 connects with Paragraph 3 because it shows the result of the changes in communication. The word "This" refers back to the changes mentioned in Paragraph 3.