A.I. Explanation:

First sentence: Why this is the first line? This paragraph is the first because it introduces the main topic. It talks about the newspapers reporting strange things happening in the heavens. This is an introductory statement that sets the scene for the rest of the text. It does not refer to any previous information, which makes it independent. Why other lines are not chosen? Paragraph 2 starts with "A Planetary Collision," which is specific and assumes prior knowledge. Paragraph 3 starts with "The leader writers," which uses a definite article and refers back to previous ideas. Paragraph 4 starts with "As a result," which shows it is not independent and needs prior context.

Concluding sentence: Why this is the last line? This paragraph is the last because it wraps up the discussion. It shows the final outcome of the excitement and expectations created by the news. The phrase "As a result" indicates that this is the conclusion of the events described earlier.

Paragraph pairs:

• Pair 1 (Paragraph 1 → Paragraph 2): Paragraph 2 connects to Paragraph 1 because it continues the topic of strange happenings. The phrase "one London paper headed the news" shows that it is a direct result of the excitement mentioned in Paragraph 1. This is a logical order of ideas.
• Pair 2 (Paragraph 2 → Paragraph 3): Paragraph 3 follows Paragraph 2 because it expands on the news from the London paper. It shows how other newspapers reacted to the same topic. This is a broader to specific strategy, where the second paragraph gives a specific news headline, and the third paragraph discusses the reactions.
• Pair 3 (Paragraph 3 → Paragraph 4): Paragraph 4 connects to Paragraph 3 because it shows the outcome of the reactions from the newspapers. The phrase "As a result" indicates that the expectation of a phenomenon in the sky is a direct result of the news discussed in Paragraph 3. This is a cause and effect relationship.