A.I. Explanation:

First sentence: Why this is the first line? This paragraph is the first sentence because it introduces the main topic, which is the Southern Pike fish. It gives a broad overview of what the text will be about. This follows the rule of Topic Sentence. Why other lines are not chosen? The other paragraphs are not chosen because they do not stand alone. For example, Paragraph 2 starts with "This enormous hungry fish" which uses a pronoun and needs context. Paragraph 3 starts with "As it kills" which also uses a pronoun. Paragraph 4 starts with "As a result" which is a transitional phrase. All these reasons make them not independent.

Concluding sentence: Why this is the last line? This paragraph is the last sentence because it wraps up the main ideas. It shows the final outcome of the Southern Pike's actions on the environment. This follows the rule of Conclusive Words.

Paragraph pairs:

• Pair 1 (Paragraph 1 → Paragraph 2): Paragraph 2 connects with Paragraph 1 because it continues the topic of the Southern Pike. The phrase "This enormous hungry fish" refers back to the Southern Pike. This follows the Noun Pronoun Rule.
• Pair 2 (Paragraph 2 → Paragraph 3): Paragraph 3 connects with Paragraph 2 because it explains the effect of the Southern Pike eating smaller fish. The phrase "As it kills all the smaller fish" shows the cause and effect relationship. This follows the Cause and Effect Relationship rule.
• Pair 3 (Paragraph 3 → Paragraph 4): Paragraph 4 connects with Paragraph 3 because it shows the result of the Southern Pike's actions. The phrase "As a result" indicates the outcome of the previous paragraph. This follows the Cause and Effect Relationship rule.