A.I. Explanation:

First sentence: Why this is the first line? This paragraph is the first sentence because it introduces the main topic of fruit orchards. It gives a broad overview of what fruit orchards are without going into details. This follows the rule of Topic Sentence. Why other lines are not chosen? Paragraph 2 starts with 'They', which is a pronoun and needs context. Paragraph 3 starts with 'The selection', which is specific and does not introduce the topic. Paragraph 4 starts with 'As a result', which shows it is not independent and needs prior information.

Concluding sentence: Why this is the last line? This paragraph is the last sentence because it wraps up the main ideas. It summarizes how the choices made in the selection of fruit varieties affect the orchard's success. This follows the rule of Summary Style.

Paragraph pairs:

• Pair 1 (Paragraph 1 → Paragraph 2): Paragraph 2 connects with Paragraph 1 because it continues the idea of fruit orchards. The phrase 'They are' refers back to 'Fruit orchards', which is the subject of Paragraph 1. This follows the Noun Pronoun Rule.
• Pair 2 (Paragraph 2 → Paragraph 3): Paragraph 3 connects with Paragraph 2 because it gives more details about how to organize orchards. The selection of fruit varieties is a specific factor that helps in the organization. This follows the Broader to Specific Strategy.
• Pair 3 (Paragraph 3 → Paragraph 4): Paragraph 4 connects with Paragraph 3 because it shows the effect of the selection of fruit varieties. The phrase 'As a result' indicates a cause and effect relationship, which follows the Cause and Effect Relationship rule.