A.I. Explanation:

First sentence: Why this is the first line? This paragraph is the first sentence because it introduces the main topic. It talks about a specific time and a person who did something important. This makes it a good starting point. It does not use any words that need other sentences for meaning. Why other lines are not chosen? Paragraph 2 starts with 'He' which is a pronoun. This means it needs more information to understand. Paragraph 3 starts with 'The result' which uses 'the' and needs prior context. Paragraph 4 starts with 'It' which is also a pronoun. Paragraph 5 starts with 'Eventually' which is a connector word. All these reasons make them not independent.

Concluding sentence: Why this is the last line? This paragraph is the last sentence because it wraps up the ideas. It shows the final outcome of the invention. It gives a big picture of how the invention changed society.

Paragraph pairs:

• Pair 1 (Paragraph 1 → Paragraph 2): This pair connects because Paragraph 2 explains what the genius did. It follows the logical order of events. The first sentence introduces the action, and the second sentence gives details about that action.
• Pair 2 (Paragraph 2 → Paragraph 3): This pair connects because Paragraph 3 talks about the result of the action in Paragraph 2. It shows a cause and effect relationship. The shaping of the stone leads to the creation of the hand-axe.
• Pair 3 (Paragraph 3 → Paragraph 4): This pair connects because Paragraph 4 explains why the hand-axe was important. It shows how the hand-axe was better than other tools. This is a logical order of ideas.
• Pair 4 (Paragraph 4 → Paragraph 5): This pair connects because Paragraph 5 shows the result of the actions in Paragraph 4. It explains how the invention of the hand-axe led to whole societies focusing on making tools.