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 Concorde. It gives a broad overview of when the Concorde started to carry passengers. It does not refer to any previous information. Why other lines are not chosen? Paragraph 2 starts with "The Concorde" which uses a definite article and assumes prior knowledge. Paragraph 3 starts with "The United States" which also uses a definite article. Paragraph 4 starts with "Beginning" which is a good start but does not introduce the main topic clearly.

Concluding sentence: Why this is the last line? This paragraph is the last sentence because it concludes the story of the Concorde. It summarizes the fate of the Concorde after its service. It brings together the earlier points about the Concorde's operation and its end.

Paragraph pairs:

• Pair 1 (Paragraph 1 → Paragraph 2): Paragraph 2 connects to Paragraph 1 because it gives more details about the Concorde. It explains who operated the Concorde and who funded it. This is a logical order from general information to specific details.
• Pair 2 (Paragraph 2 → Paragraph 3): Paragraph 3 connects to Paragraph 2 because it shifts the focus to the United States. It shows a contrast between the Concorde and the U.S. program. This is a logical order because it compares two different approaches to supersonic transport.
• Pair 3 (Paragraph 3 → Paragraph 4): Paragraph 4 connects to Paragraph 3 because it continues the story of supersonic transport. It shows the outcome of the Concorde's service after discussing the U.S. program. This is a logical order because it explains what happened to the Concorde after its introduction.