First sentence: Why this is the first line? This paragraph is the first sentence because it is a general statement about change. It introduces the main topic without needing other sentences for 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 "People" which is a specific subject and needs context. Paragraph 3 starts with "For example" which shows it is not independent. Paragraph 4 starts with "Furthermore" which is a conjunction and needs a previous sentence.

Concluding sentence: Why this is the last line? This paragraph is the last sentence because it wraps up the ideas about changes to the earth. It adds more information and shows the result of the changes discussed in the previous paragraphs.

Paragraph pairs:

• Pair 1 (Paragraph 1 → Paragraph 2): Paragraph 2 connects to Paragraph 1 because it explains how the earth is changing. It shows the cause of the change by stating what people and machines are doing.
• Pair 2 (Paragraph 2 → Paragraph 3): Paragraph 3 connects to Paragraph 2 because it gives examples of how the land is reshaped. It uses "For example" to show that it is providing specific details about the work mentioned in Paragraph 2.
• Pair 3 (Paragraph 3 → Paragraph 4): Paragraph 4 connects to Paragraph 3 because it continues to give examples of how the land is changed. It uses "Furthermore" to add more information about the changes.