A.I. Explanation:

First sentence: Why this is the first line? This paragraph is the first sentence because it introduces the main topic of planning for a long-distance hike. It sets up the theme of preparation without going into details. It uses the phrase 'Before embarking' which shows it is about the initial steps needed. Why other lines are not chosen? The other paragraphs do not qualify as the first sentence. For example, Paragraph 2 starts with 'I also dedicated', which uses a pronoun 'I' that refers back to a person, making it dependent. Paragraph 3 starts with 'After months of preparation', which indicates it is not the beginning but a continuation. Paragraph 4 starts with 'Packing the right gear', which is specific and assumes prior knowledge.

Concluding sentence: Why this is the last line? This paragraph is the last sentence because it wraps up the whole story. It shows the final action after all the planning and preparation. The phrase 'the day finally arrived' signals the end of the preparation and the start of the hike.

Paragraph pairs:

• Pair 1 (Paragraph 1 → Paragraph 2): Paragraph 2 connects to Paragraph 1 because it continues the idea of preparation. The phrase 'I also dedicated weeks' shows that the writer is talking about their personal preparation, which follows the need to plan.
• Pair 2 (Paragraph 2 → Paragraph 3): Paragraph 3 links to Paragraph 2 because it talks about another important part of preparation. The phrase 'Packing the right gear is crucial' shows that after physical fitness, the next step is to gather the right equipment.
• Pair 3 (Paragraph 3 → Paragraph 4): Paragraph 4 connects to Paragraph 3 because it shows the result of all the preparation. The phrase 'After months of preparation' indicates that the packing leads to the actual hike.