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, which is silk. It gives a broad overview of what silk is and how it is made. It does not refer to any previous information, so it stands alone. This follows the rule of Topic Sentence. 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 "Legend has it" which is not a general statement. - Paragraph 3 starts with "One account of the story goes" which refers to a specific story. - Paragraph 4 starts with "She collected" which uses a pronoun and needs context. - Paragraph 5 starts with "It just so happened" which is not a general statement.

Concluding sentence: Why this is the last line? This paragraph is the last sentence because it wraps up the story by showing the result of her actions with the cocoons. It gives a final detail about how silk is made from the cocoons. This follows the Summary Style rule.

Paragraph pairs:

• Pair 1 (Paragraph 1 → Paragraph 2): Paragraph 2 connects to Paragraph 1 because it gives information about who discovered silkworms, which relates to the topic of silk. This follows the Logical Order rule.
• Pair 2 (Paragraph 2 → Paragraph 3): Paragraph 3 connects to Paragraph 2 because it tells more about the story of Lei Tzu and what she discovered. This follows the Broader to Specific Strategy.
• Pair 3 (Paragraph 3 → Paragraph 4): Paragraph 4 connects to Paragraph 3 because it shows what she did after discovering the silkworms. This follows the Logical Order rule.
• Pair 4 (Paragraph 4 → Paragraph 5): Paragraph 5 connects to Paragraph 4 because it describes what happened next with the cocoons she collected. This follows the Chronological Order rule.