A.I. Explanation:

First sentence: Why this is the first line? This paragraph is the first sentence because it introduces the main topic of packing. It gives a clear overview of what to do before packing. It does not refer to any previous information. Why other lines are not chosen? Paragraph 2 starts with 'Packing light', which assumes prior knowledge. Paragraph 3 starts with 'Before you start packing', but it is not independent because it refers to the action of packing. Paragraph 4 starts with 'Once your bag is packed', which also assumes prior context.

Concluding sentence: Why this is the last line? This paragraph is the last sentence because it wraps up the packing process. It gives a final action to take after packing, which concludes the topic.

Paragraph pairs:

• Pair 1 (Paragraph 1 → Paragraph 2): Paragraph 2 connects with Paragraph 1 because it continues the topic of packing. It explains why packing light is important after making a list.
• Pair 2 (Paragraph 2 → Paragraph 3): Paragraph 3 links to Paragraph 2 by giving an example of how to pack light. It shows a specific way to save space.
• Pair 3 (Paragraph 3 → Paragraph 4): Paragraph 4 follows Paragraph 3 because it gives a final step after packing. It suggests checking the bag to remove unnecessary items.