A.I. Explanation:

First sentence: Why this is the first line? This paragraph is the first line because it introduces the main topic of violence and racial prejudice. It sets the stage for the discussion without needing any prior context. It does not use any pronouns or definite articles that refer to previous ideas. Why other lines are not choosen? Paragraph 2 starts with "There are countries" which makes it dependent on prior context. Paragraph 3 starts with a question, which is not independent. Paragraph 4 uses "we" which refers back to a group, making it dependent. Paragraph 5 uses "who" which also refers back to people mentioned before, making it dependent.

Concluding sentence: Why this is the last line? This paragraph is the last line because it wraps up the discussion. It reflects on the main theme of unchanged instincts despite appearances. It gives a final thought on the topic, making it a strong conclusion.

Paragraph pairs:

• Pair 1 (Paragraph 1 → Paragraph 2): Paragraph 2 connects with Paragraph 1 because it continues the topic of violence in different countries. It shows examples of how violence is used, which follows the introduction in Paragraph 1. This is a logical order.
• Pair 2 (Paragraph 2 → Paragraph 3): Paragraph 3 connects with Paragraph 2 because it discusses how people justify violence. It shows that even reasonable people support violence, which relates to the examples of violence in Paragraph 2. This is a logical flow of ideas.
• Pair 3 (Paragraph 3 → Paragraph 4): Paragraph 4 connects with Paragraph 3 because it expresses despair about the situation. It shows that despite arguments for violence, there is no real progress. This follows the discussion of people's views on violence.
• Pair 4 (Paragraph 4 → Paragraph 5): Paragraph 5 connects with Paragraph 4 because it continues the theme of unchanged human nature. It shows that even with changes in appearance, our basic instincts are the same. This is a logical conclusion to the despair expressed in Paragraph 4.