First sentence: Why this is the first line? This paragraph is the first sentence because it introduces the main topic. It talks about the ancient Greeks and their observations of stars. This is an overview of what the text will discuss. It does not use any words that need prior context. Why other lines are not chosen? Paragraph 2 starts with "They" which is a pronoun and needs context. Paragraph 3 starts with "A few thousand years later" which shows a time order and needs a previous sentence. Paragraph 4 starts with "Rovers" which is specific and needs context. Paragraph 5 starts with "The questions" which also needs prior information.

Concluding sentence: Why this is the last line? This paragraph is the last sentence because it wraps up the main ideas. It reflects on the questions that have been asked throughout history about the solar system. It gives a conclusion to the discussion.

Paragraph pairs:

• Pair 1 (Paragraph 1 → Paragraph 2): Paragraph 2 connects with Paragraph 1 because it explains what the ancient Greeks saw. The word "They" refers back to the Greeks. This shows a clear link between the two sentences.
• Pair 2 (Paragraph 2 → Paragraph 3): Paragraph 3 connects with Paragraph 2 because it talks about humanity becoming wanderers too. The word "them" in Paragraph 3 refers back to "wanderers" in Paragraph 2. This shows a logical flow of ideas.
• Pair 3 (Paragraph 3 → Paragraph 4): Paragraph 4 connects with Paragraph 3 because it gives examples of the robots that humanity sends to explore. This shows a clear progression from the idea of humanity as wanderers to specific examples of exploration.
• Pair 4 (Paragraph 4 → Paragraph 5): Paragraph 5 connects with Paragraph 4 because it discusses the questions that these robots ask. It shows a logical order from examples of exploration to the questions that arise from that exploration.