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 the birthday. It gives a broad overview of what happened first. It does not use any pronouns or definite articles that refer to previous ideas. Why other lines are not chosen? Paragraph 2 starts with "The decorations" which uses the definite article "the" and assumes prior knowledge. Paragraph 3 starts with "Invitations" which is also a specific noun. Paragraph 4 starts with "As the day approached" which refers to a time that needs context. Paragraph 5 starts with "Finally" which suggests it is not the first sentence.

Concluding sentence: Why this is the last line? This paragraph is the last sentence because it wraps up the whole story. It shows the result of all the planning and efforts made for the birthday surprise. It gives a clear conclusion to the events.

Paragraph pairs:

• Pair 1 (Paragraph 1 → Paragraph 2): Paragraph 2 connects to Paragraph 1 because it continues the topic of planning. The first paragraph talks about planning, and the second paragraph gives details about decorations, which are part of the planning process. This shows a logical order.
• Pair 2 (Paragraph 2 → Paragraph 3): Paragraph 3 connects to Paragraph 2 because it continues the theme of preparation for the birthday. After discussing decorations, it makes sense to talk about invitations next. This shows a logical order.
• Pair 3 (Paragraph 3 → Paragraph 4): Paragraph 4 connects to Paragraph 3 because it follows the timeline of events. After sending invitations, the next step is to prepare for the day of the surprise. This shows a chronological order.
• Pair 4 (Paragraph 4 → Paragraph 5): Paragraph 5 connects to Paragraph 4 because it describes the outcome of all the planning and preparation. After the distractions, the next part is the success of the surprise. This shows a logical order.