A.I. Explanation:

First sentence: Why this is the first line? This paragraph is the first sentence because it introduces the main topic of the wedding. It does not need another sentence for context. It talks about the idea of an eco-friendly wedding, which is broad and sets the stage for the rest of the text. This follows the rule of Topic Sentence. 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 'They', which is a pronoun and needs context. Paragraph 3 starts with 'To make', which is a conjunction. Paragraph 4 starts with 'Ultimately', which is also a transitional word. These reasons make them not independent.

Concluding sentence: Why this is the last line? This paragraph is the last sentence because it concludes the text. It summarizes the main ideas and reflects on the couple's commitment to the environment. It uses the phrase 'Ultimately', which signals the end of the discussion.

Paragraph pairs:

• Pair 1 (Paragraph 1 → Paragraph 2): Paragraph 2 connects with Paragraph 1 because it continues the topic of eco-friendliness. The phrase 'They selected a venue' shows a logical order from the idea of an eco-friendly wedding to the action they took.
• Pair 2 (Paragraph 2 → Paragraph 3): Paragraph 3 connects with Paragraph 2 because it shows another step in their planning. After choosing a venue, they decided on a menu. This shows a logical order of actions.
• Pair 3 (Paragraph 3 → Paragraph 4): Paragraph 4 connects with Paragraph 3 because it wraps up the ideas. After discussing the menu, it talks about the overall meaning of the wedding. This shows a logical order from specific details to a broader conclusion.