A.I. Explanation:

First sentence: Why this is the first line? This paragraph is the first line because it introduces the main topic of the text, which is about a change in weather. It sets the scene without needing any prior context. It does not use any pronouns or definite articles that refer to previous ideas. Why other lines are not chosen? Paragraph 2 starts with "A year earlier," which needs context from the previous sentence. Paragraph 3 starts with "The Earth literally darkened," which assumes prior mention of the cause. Paragraph 4 starts with "This, of course," which refers back to something not yet mentioned. Paragraph 5 starts with "Between May and August 1783," which also needs context.

Concluding sentence: Why this is the last line? This paragraph is the last line because it provides a historical example that wraps up the discussion. It gives a clear ending to the topic by showing another significant volcanic event.

Paragraph pairs:

• Pair 1 (Paragraph 1 → Paragraph 2): This pair connects because Paragraph 2 gives background information about the volcano that caused the weather change in Paragraph 1. It follows a logical order where the cause (the volcano) comes after the effect (the weather change).
• Pair 2 (Paragraph 2 → Paragraph 3): This pair connects because Paragraph 3 describes the effects of the volcanic dust mentioned in Paragraph 2. It shows a cause and effect relationship where the eruption leads to the darkening of the Earth.
• Pair 3 (Paragraph 3 → Paragraph 4): This pair connects because Paragraph 4 explains the significance of the events described in Paragraph 3. It provides a broader context and shows that the darkening of the Earth was an extraordinary event.
• Pair 4 (Paragraph 4 → Paragraph 5): This pair connects because Paragraph 5 gives an example of a similar event that happened before the one discussed in Paragraph 4. It follows a logical order where the discussion of past events comes after explaining the significance of the current event.