A.I. Explanation:

First sentence: Why this is the first line? This paragraph is the first because it introduces the main topic of the text. It talks about a fear during the Second World War. This sets the stage for the following information about the road. It does not refer to any previous information, so it is independent. Why other lines are not chosen? Paragraph 2 starts with "An overland road link..." which is specific and does not stand alone. Paragraph 3 starts with "Ten thousand engineers..." which is also specific. Paragraph 4 starts with "By the following spring..." which assumes prior knowledge. Paragraph 5 starts with "The Alaska Highway..." which is also specific and assumes knowledge of the highway.

Concluding sentence: Why this is the last line? This paragraph is the last because it wraps up the story. It shows the final result of all the actions taken in the previous paragraphs. It gives a clear conclusion to the topic.

Paragraph pairs:

• Pair 1 (Paragraph 1 → Paragraph 2): Paragraph 2 connects to Paragraph 1 because it shows the action taken after the fear mentioned in Paragraph 1. It follows a logical order where the fear leads to planning a road.
• Pair 2 (Paragraph 2 → Paragraph 3): Paragraph 3 connects to Paragraph 2 because it gives details about the building of the road mentioned in Paragraph 2. It follows a broader to specific strategy, where the planning leads to the actual work done.
• Pair 3 (Paragraph 3 → Paragraph 4): Paragraph 4 connects to Paragraph 3 because it talks about what happened after the road was built. It shows a cause and effect relationship where the building of the road leads to the need for bridges.
• Pair 4 (Paragraph 4 → Paragraph 5): Paragraph 5 connects to Paragraph 4 because it concludes the story by showing the final result of the road and bridges. It follows a logical order where the replacement of bridges leads to the linking of highways.