A.I. Explanation:

First sentence: Why this is the first line? This paragraph is the first sentence because it introduces the main topic of tipping restaurant staff. It is a general statement that does not need other sentences for context. It sets up the theme of the text without going into details. Why other lines are not chosen? The other paragraphs are not chosen because they do not meet the criteria for being independent. For example, Paragraph 2 starts with 'This custom,' which refers back to the idea of tipping, so it cannot stand alone. Paragraph 3 starts with 'When determining,' which shows it is not a general statement. Paragraph 4 uses 'Adequate tipping,' which is specific and assumes prior knowledge. Paragraph 5 starts with 'Finally,' which shows it is not independent.

Concluding sentence: Why this is the last line? This paragraph is the last sentence because it gives a final recommendation about tipping. It wraps up the text by providing practical advice. The word 'Finally' shows that this is the end of the discussion.

Paragraph pairs:

• Pair 1 (Paragraph 1 → Paragraph 2): Paragraph 2 connects with Paragraph 1 because it explains more about the custom of tipping. It shows how tipping helps restaurant staff. This is a logical order because the first paragraph introduces the topic, and the second gives more details.
• Pair 2 (Paragraph 2 → Paragraph 3): Paragraph 3 connects with Paragraph 2 because it talks about how to decide the right amount to tip. It follows logically because after explaining why tipping is important, it gives advice on how to tip.
• Pair 3 (Paragraph 3 → Paragraph 4): Paragraph 4 connects with Paragraph 3 because it explains the benefits of tipping well. After discussing how to determine the tip amount, it shows that good tipping encourages better service.
• Pair 4 (Paragraph 4 → Paragraph 5): Paragraph 5 connects with Paragraph 4 because it gives practical advice on how to tip. After discussing the importance of tipping well, it suggests using local currency to save money when tipping.