A.I. Explanation:

First sentence: Why this is the first line? This paragraph is the first line because it introduces the main topic of rainforests. It gives a broad overview of what rainforests are and their age. It does not refer to any previous information. Why other lines are not chosen? Paragraph 2 starts with "These forests" which refers back to rainforests, so it cannot be first. Paragraph 3 starts with "The dense canopy" which also refers to rainforests. Paragraph 4 starts with "However" which is a conjunction and shows a continuation of thought, so it cannot be first.

Concluding sentence: Why this is the last line? This paragraph is the last line because it concludes the discussion about rainforests by highlighting a serious issue they face. It summarizes the main points and shows the impact of deforestation.

Paragraph pairs:

• Pair 1 (Paragraph 1 → Paragraph 2): Paragraph 2 connects to Paragraph 1 because it continues the topic of rainforests. It gives more specific information about their coverage and biodiversity. This follows the Broader to Specific Strategy.
• Pair 2 (Paragraph 2 → Paragraph 3): Paragraph 3 connects to Paragraph 2 because it describes a specific feature of rainforests, the dense canopy. This follows the Logical Order as it continues the discussion about the characteristics of rainforests.
• Pair 3 (Paragraph 3 → Paragraph 4): Paragraph 4 connects to Paragraph 3 because it introduces a problem related to rainforests. The threat of deforestation follows logically after discussing the features of rainforests. This follows the Cause and Effect Relationship.