A.I. Explanation:

First sentence: Why this is the first line? This paragraph is the first sentence because it introduces the main topic of ethics. It gives a broad overview of what ethics is about without going into details. It does not use any pronouns or definite articles that would need prior context. Why other lines are not chosen? Paragraph 2 starts with 'It', which is a pronoun and needs context. Paragraph 3 starts with 'Different', which is not general. Paragraph 4 starts with 'For instance', which shows it is an example and not a main idea. Paragraph 5 starts with 'In contrast', which shows it is comparing and needs a previous idea.

Concluding sentence: Why this is the last line? This paragraph is the last sentence because it wraps up the discussion on ethical theories. It contrasts with the previous example, showing a different viewpoint. This gives a clear conclusion to the topic of ethics.

Paragraph pairs:

• Pair 1 (Paragraph 1 → Paragraph 2): Paragraph 2 connects with Paragraph 1 because it continues the topic of ethics. The phrase 'It explores' refers back to 'Ethics', showing a clear link. This is a Noun Pronoun Rule.
• Pair 2 (Paragraph 2 → Paragraph 3): Paragraph 3 connects with Paragraph 2 because it gives more details about ethics. The phrase 'Different ethical theories' shows a logical order from general concepts to specific theories.
• Pair 3 (Paragraph 3 → Paragraph 4): Paragraph 4 connects with Paragraph 3 because it gives an example of one ethical theory. The phrase 'For instance' shows that it is providing a specific case of the theories mentioned.
• Pair 4 (Paragraph 4 → Paragraph 5): Paragraph 5 connects with Paragraph 4 because it presents a different ethical theory. The phrase 'In contrast' shows that it is comparing deontological ethics with utilitarianism, which is a clear logical order.