A.I. Explanation:

First sentence: Why this is the first line? This paragraph is the first sentence because it introduces the main topic of great white sharks. It gives a broad overview of where they are found and their importance as the largest predatory fish. It does not need any other sentence for context. Why other lines are not chosen? Paragraph 2 starts with 'They', which is a pronoun and needs context. Paragraph 3 starts with 'There is', which does not introduce the topic. Paragraph 4 starts with 'Overfishing', which is specific and does not introduce the main topic. Paragraph 5 starts with 'Therefore', which shows it is a conclusion and needs prior information.

Concluding sentence: Why this is the last line? This paragraph is the last sentence because it wraps up the discussion about great white sharks. It uses the word 'Therefore', which shows it is a conclusion based on the previous information.

Paragraph pairs:

• Pair 1 (Paragraph 1 → Paragraph 2): This pair connects because Paragraph 2 gives specific information about the size of great white sharks. It follows the general statement in Paragraph 1 about their importance.
• Pair 2 (Paragraph 2 → Paragraph 3): This pair connects because Paragraph 3 talks about the population of great white sharks. It follows the information about their size and leads to concerns about their numbers.
• Pair 3 (Paragraph 3 → Paragraph 4): This pair connects because Paragraph 4 explains the threats to great white sharks. It follows the concern about their decreasing numbers.
• Pair 4 (Paragraph 4 → Paragraph 5): This pair connects because Paragraph 5 concludes the discussion by stating the result of the threats mentioned in Paragraph 4. It shows the consequence of the threats.