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 tells us what the site is about without needing any other information. This follows the rule of Topic Sentence. Why other lines are not chosen? The other paragraphs do not qualify as the first sentence. For example, Paragraph 2 starts with "The site" which is not independent because it refers back to the site mentioned in Paragraph 1. Paragraph 3 starts with "There is" which is not independent because it does not introduce a new idea. Paragraph 4 starts with "The material" which also refers back to previous information.

Concluding sentence: Why this is the last line? This paragraph is the last sentence because it wraps up the information about the site. It gives a final point about what is missing from the site. This follows the rule of Conclusive Words.

Paragraph pairs:

• Pair 1 (Paragraph 1 → Paragraph 2): Paragraph 2 connects to Paragraph 1 because it gives more details about the site. This follows the Broader to Specific Strategy. The first sentence talks about the site, and the second sentence explains what is listed on that site.
• Pair 2 (Paragraph 2 → Paragraph 3): Paragraph 3 connects to Paragraph 2 because it explains how the materials are organised. This follows the Logical Order rule. The second sentence lists the materials, and the third sentence tells us how they are arranged.
• Pair 3 (Paragraph 3 → Paragraph 4): Paragraph 4 connects to Paragraph 3 because it gives a limitation about the site. This follows the Cause and Effect Relationship rule. The third sentence explains how the material is organised, and the fourth sentence tells us that there is no way to search for it.