A.I. Explanation:

First sentence: Why this is the first line? This paragraph is the first because it introduces William Smith and his interest in rocks and fossils. It is a general statement that sets the topic. It does not use any words that need prior context. Why other lines are not chosen? Paragraph 2 starts with "By the time he retired," which needs context from earlier sentences. Paragraph 3 starts with "He entered the workforce," which also needs context. Paragraph 4 starts with "This work allowed him," which refers back to previous information.

Concluding sentence: Why this is the last line? This paragraph is the last because it summarizes Smith's achievements. It wraps up the story of his life and work.

Paragraph pairs:

• Pair 1 (Paragraph 1 → Paragraph 2): Paragraph 2 connects to Paragraph 1 because it shows what Smith did after his interest in rocks and fossils. This is a logical order of events.
• Pair 2 (Paragraph 2 → Paragraph 3): Paragraph 3 follows Paragraph 2 because it explains the result of his work. It shows how studying canals helped him travel.
• Pair 3 (Paragraph 3 → Paragraph 4): Paragraph 4 connects to Paragraph 3 because it shows what he achieved after his travels. It gives the outcome of his work.