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, which is Johannes Gutenberg and his role in printing. It does not need another sentence for context. It gives a broad overview of who Gutenberg is and what he did. Why other lines are not chosen? Paragraph 2 starts with 'This type of printing,' which needs context from the previous sentence. Paragraph 3 starts with 'It also played,' which refers back to something not yet mentioned. Paragraph 4 starts with 'His introduction,' which also needs prior context.

Concluding sentence: Why this is the last line? This paragraph is the last sentence because it summarizes the impact of printing. It gives a final thought about how printing influenced important areas like science and the economy. This wraps up the main ideas of the text.

Paragraph pairs:

• Pair 1 (Paragraph 1 → Paragraph 2): Paragraph 2 connects with Paragraph 1 because it continues the idea of Gutenberg's work. The phrase 'His introduction' refers back to Gutenberg's action in the first paragraph. This shows a clear logical order.
• Pair 2 (Paragraph 2 → Paragraph 3): Paragraph 3 connects with Paragraph 2 because it explains the importance of the printing introduced in Paragraph 2. The phrase 'This type of printing' refers back to the printing mentioned before, showing a clear connection.
• Pair 3 (Paragraph 3 → Paragraph 4): Paragraph 4 connects with Paragraph 3 because it gives more details about the impact of the printing. The word 'It' refers back to 'This type of printing,' showing a logical flow of ideas.