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 seeds sprouting, which is the beginning of the process. This follows the rule of Topic Sentence. Why other lines are not chosen? Other paragraphs are not chosen because they do not stand alone. For example, Paragraph 2 starts with 'They', which is a pronoun and needs context. Paragraph 3 starts with 'Farmland', which is a specific subject and not general. Paragraph 4 starts with 'The saplings', which also uses a definite article and needs prior context. Paragraph 5 starts with 'If', which is a conjunction and cannot be first.

Concluding sentence: Why this is the last line? This paragraph is the last sentence because it wraps up the whole idea. It shows what happens if the farmland is not used, which brings the topic to a close.

Paragraph pairs:

• Pair 1 (Paragraph 1 → Paragraph 2): Paragraph 2 connects with Paragraph 1 because it continues the idea of growth. The phrase 'They grow' shows a logical order from seedlings to saplings.
• Pair 2 (Paragraph 2 → Paragraph 3): Paragraph 3 connects with Paragraph 2 because it continues the topic of saplings. It shows the next step in growth, which is a logical order.
• Pair 3 (Paragraph 3 → Paragraph 4): Paragraph 4 connects with Paragraph 3 because it introduces a new idea about forests. It shows a contrast between growing trees and creating farmland.
• Pair 4 (Paragraph 4 → Paragraph 5): Paragraph 5 connects with Paragraph 4 because it talks about what happens after farmland is created. It shows a cause and effect relationship.