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. It gives a broad overview of what biodiversity means without going into specifics. This follows the rule of Topic Sentence. Why other lines are not chosen? Paragraph 2 starts with 'Biodiversity is essential...' which is a specific statement and does not introduce the topic. Paragraph 3 starts with 'Unfortunately...' which shows a problem and does not introduce the topic. Paragraph 4 starts with 'As a result...' which indicates a consequence and does not stand alone.

Concluding sentence: Why this is the last line? This paragraph is the last sentence because it wraps up the discussion about biodiversity and its consequences. It shows the impact of human activities on the environment, which concludes the topic. This follows the rule of Conclusive Words.

Paragraph pairs:

• Pair 1 (Paragraph 1 → Paragraph 2): Paragraph 2 connects with Paragraph 1 because it continues the topic of biodiversity. It explains why biodiversity is important. This follows the Broader to Specific Strategy.
• Pair 2 (Paragraph 2 → Paragraph 3): Paragraph 3 connects with Paragraph 2 because it shows a problem related to biodiversity. It explains the risk of extinction, which is a consequence of losing biodiversity. This follows the Cause and Effect Relationship.
• Pair 3 (Paragraph 3 → Paragraph 4): Paragraph 4 connects with Paragraph 3 because it explains the result of the loss of biodiversity. It shows how human activities are affecting the environment. This follows the Cause and Effect Relationship.