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 text. It talks about the Egyptians and their early attempt at making a book. This is an important starting point. It does not use any words that need prior context, so it stands alone. Why other lines are not chosen? The other paragraphs are not chosen because they do not meet the criteria for being independent. For example, Paragraph 2 starts with 'But', which is a conjunction. Paragraph 3 starts with 'The', which refers back to something already mentioned. Paragraph 4 starts with 'But', which is also a conjunction. Paragraph 5 starts with 'This', which is a pronoun that refers back to something else.

Concluding sentence: Why this is the last line? This paragraph is the last sentence because it wraps up the discussion about parchment. It gives a final detail about what parchment is made from and its advantages. This is a summary style that brings together the earlier points.

Paragraph pairs:

• Pair 1 (Paragraph 1 → Paragraph 2): This pair connects because Paragraph 2 gives more detail about what the Egyptians used to make their books. It follows the Broader to Specific Strategy. The first sentence is general about the Egyptians, and the second sentence specifies what they used.
• Pair 2 (Paragraph 2 → Paragraph 3): This pair connects because Paragraph 3 continues the topic of papyrus. It shows that the Romans also used papyrus. This follows the Logical Order rule, as it moves from the Egyptians to the Romans.
• Pair 3 (Paragraph 3 → Paragraph 4): This pair connects because Paragraph 4 explains a problem with using large rolls of papyrus. It uses the Connector strategy with 'But' to show a contrast between using rolls and the need for parchment.
• Pair 4 (Paragraph 4 → Paragraph 5): This pair connects because Paragraph 5 explains what parchment is and why it is better. It follows the Cause and Effect Relationship rule, as the need for parchment is caused by the difficulty of using rolls.