A.I. Explanation:

First sentence: Why this is the first line? This paragraph is the first sentence because it introduces the main topic. It gives a broad overview of the research about negotiators. It does not use any words that need prior context. Why other lines are not choosen? The other paragraphs are not chosen because they do not stand alone. For example, Paragraph 2 starts with 'This happens', which needs context. Paragraph 3 starts with 'Think back', which is also not independent. Paragraph 4 starts with 'I may have suggested', which is a personal statement and needs context. Paragraph 5 uses 'A difference', which assumes prior knowledge.

Concluding sentence: Why this is the last line? This paragraph is the last sentence because it wraps up the main idea. It gives a conclusion about counter proposing and its effectiveness.

Paragraph pairs:

• Pair 1 (Paragraph 1 → Paragraph 2): Paragraph 2 connects with Paragraph 1 because it uses the connector 'This happens'. It shows that the research applies to real life.
• Pair 2 (Paragraph 2 → Paragraph 3): Paragraph 3 connects with Paragraph 2 because it gives an example of everyday life. It shows how the idea from Paragraph 2 is true in a specific situation.
• Pair 3 (Paragraph 3 → Paragraph 4): Paragraph 4 connects with Paragraph 3 because it gives another example of a counter proposal. It continues the theme of negotiation in everyday situations.
• Pair 4 (Paragraph 4 → Paragraph 5): Paragraph 5 connects with Paragraph 4 because it summarizes the main idea about counter proposing. It shows the difference between skilled and average negotiators.