A.I. Explanation:

First sentence: Why this is the first line? This paragraph is the first line because it introduces the main topic of the text, which is about planning a trip. It sets up the theme of choosing a destination without needing other sentences for context. This follows the rule of Topic Sentence. Why other lines are not chosen? The other paragraphs are not chosen because they do not stand alone. For example, Paragraph 2 starts with 'Once the destination is decided,' which needs prior context. Paragraph 3 starts with 'Before setting off,' which also needs context. Paragraph 4 starts with 'Packing the car,' which is not general and assumes prior knowledge.

Concluding sentence: Why this is the last line? This paragraph is the last line because it wraps up the ideas about preparing for a trip. It gives a final step that is important before starting the journey.

Paragraph pairs:

• Pair 1 (Paragraph 1 → Paragraph 2): Paragraph 2 connects with Paragraph 1 because it continues the idea of planning a trip. The phrase 'Once the destination is decided' shows a logical order of steps in trip planning.
• Pair 2 (Paragraph 2 → Paragraph 3): Paragraph 3 connects with Paragraph 2 because it follows the logical order of preparing for a trip. After planning the itinerary, checking the vehicle is the next step.
• Pair 3 (Paragraph 3 → Paragraph 4): Paragraph 4 connects with Paragraph 3 because it continues the theme of preparation. After checking the vehicle, packing is another important step before leaving.