A.I. Explanation:

First sentence: Why this is the first line? This paragraph is the first sentence because it introduces the main topic of biodiversity and trees. It is a general statement that does not need another sentence for context. It sets up the main idea without going into details. Why other lines are not chosen? Paragraph 2 starts with 'They', which is a pronoun that refers back to trees, so it cannot be independent. Paragraph 3 starts with 'Additionally', which is a conjunction and shows it is not independent. Paragraph 4 starts with 'Conversely', which is also a conjunction and shows it is not independent.

Concluding sentence: Why this is the last line? This paragraph is the last sentence because it wraps up the discussion about trees and biodiversity. It shows the negative effect of removing trees, which concludes the topic. The word 'Conversely' signals a change in direction, making it clear that this is the final point.

Paragraph pairs:

• Pair 1 (Paragraph 1 → Paragraph 2): Paragraph 2 connects with Paragraph 1 because it explains how trees help biodiversity. The word 'They' refers back to 'trees', showing a clear link. This is a Noun Pronoun Rule.
• Pair 2 (Paragraph 2 → Paragraph 3): Paragraph 3 connects with Paragraph 2 because it adds more information about trees. The word 'Additionally' shows that it is giving more details about the topic. This is a Connector Strategy.
• Pair 3 (Paragraph 3 → Paragraph 4): Paragraph 4 connects with Paragraph 3 because it shows a contrast. The word 'Conversely' indicates that it is talking about the opposite effect of removing trees. This is a Contrast Rule.