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 the Black Death. It gives a broad overview of the event without going into details. It does not use any pronouns or definite articles that would need prior context. Why other lines are not chosen? Paragraph 2 starts with "It" which is a pronoun, so it needs context. Paragraph 3 starts with "This pandemic" which also uses a pronoun. Paragraph 4 starts with "As a result" which is a transitional phrase. All these reasons make them 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 summarizes the overall impact of the Black Death, showing how it changed society. The phrase "As a result" signals that this is the conclusion of the discussion.

Paragraph pairs:

• Pair 1 (Paragraph 1 → Paragraph 2): Paragraph 2 connects with Paragraph 1 because it continues the topic of the Black Death. It gives a specific detail about the number of people it killed. This shows a logical order from a general statement to a specific fact.
• Pair 2 (Paragraph 2 → Paragraph 3): Paragraph 3 connects with Paragraph 2 because it explains the effects of the deaths caused by the Black Death. This shows a cause and effect relationship, where the deaths led to social and economic changes.
• Pair 3 (Paragraph 3 → Paragraph 4): Paragraph 4 connects with Paragraph 3 because it shows the results of the effects mentioned in Paragraph 3. The phrase "As a result" indicates that the transformations are a direct outcome of the previous effects.