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 clearly states the importance of book reviews and literary criticism. This follows the rule of Topic Sentence. It does not refer to any previous information, making it independent. 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 "On the one hand," which is a conjunction. Paragraph 3 does not stand alone because it refers back to the topic. Paragraph 4 also starts with "Thus," which shows it is not independent.

Concluding sentence: Why this is the last line? This paragraph is the last sentence because it wraps up the main ideas of the text. It uses the word "Thus," which signals a conclusion. It brings together the points made about reviews and criticism.

Paragraph pairs:

• Pair 1 (Paragraph 1 → Paragraph 2): Paragraph 2 connects with Paragraph 1 because it uses the connector "On the one hand." This shows that it is giving one side of the argument about the role of reviews.
• Pair 2 (Paragraph 2 → Paragraph 3): Paragraph 3 connects with Paragraph 2 because it uses the connector "On the other hand." This shows that it is giving the other side of the argument about the role of literary criticism.
• Pair 3 (Paragraph 3 → Paragraph 4): Paragraph 4 connects with Paragraph 3 because it summarizes the points made in the previous paragraphs. The word "Thus" shows that it is concluding the discussion.