First sentence: Why this is the first line? This paragraph is the first sentence because it introduces the main topic. It talks about the mass extinction of dinosaurs and the reason for it. This is a broad overview of the subject. It does not use any words that need prior context. Why other lines are not chosen? Paragraph 2 starts with 'Within minutes', which needs context from the first sentence. Paragraph 3 starts with 'The force', which also needs context. Paragraph 4 starts with 'Models measuring', which is not a general statement. All these sentences cannot stand alone.

Concluding sentence: Why this is the last line? This paragraph is the last sentence because it summarizes the overall impact of the events. It brings together the earlier points about the tsunami and its effects on the planet.

Paragraph pairs:

• Pair 1 (Paragraph 1 → Paragraph 2): Paragraph 2 connects with Paragraph 1 because it uses the word 'this collision'. This shows a cause and effect relationship. The tsunami happens because of the asteroid crash.
• Pair 2 (Paragraph 2 → Paragraph 3): Paragraph 3 connects with Paragraph 2 because it continues the story of the tsunami. It explains what happens next after the tsunami is triggered. This shows a logical order of events.
• Pair 3 (Paragraph 3 → Paragraph 4): Paragraph 4 connects with Paragraph 3 because it talks about the results of the tsunami. It explains the destruction caused by the wave. This shows a broader to specific strategy.