A.I. Explanation:

First sentence: Why this is the first line? This paragraph is the first sentence because it introduces the main topic of desert animals and insects. It gives a broad overview of how they survive in the desert. It does not use any words that need prior context. Why other lines are not chosen? Paragraph 2 starts with 'Often,' which is a transitional word, so it cannot be first. Paragraph 3 starts with 'Animals such as,' which is not general enough to stand alone. Paragraph 4 starts with 'The Australian desert toad,' which uses 'the' and assumes prior knowledge. Paragraph 5 starts with 'Camels,' which also assumes prior knowledge.

Concluding sentence: Why this is the last line? This paragraph is the last sentence because it wraps up the discussion about how desert animals survive. It gives a final example of an animal and its unique way of coping with the desert conditions.

Paragraph pairs:

• Pair 1 (Paragraph 1 → Paragraph 2): Paragraph 2 connects with Paragraph 1 because it continues the idea of how desert animals survive. It uses the connector 'Often,' which shows a logical flow from the first paragraph.
• Pair 2 (Paragraph 2 → Paragraph 3): Paragraph 3 connects with Paragraph 2 because it gives specific examples of animals that survive in the desert. This follows the broader idea of survival from the previous paragraph.
• Pair 3 (Paragraph 3 → Paragraph 4): Paragraph 4 connects with Paragraph 3 because it continues to discuss how different animals cope with water in the desert. It provides more specific examples, which follows the general statement in the previous paragraph.
• Pair 4 (Paragraph 4 → Paragraph 5): Paragraph 5 connects with Paragraph 4 because it introduces another animal, camels, and discusses their way of surviving in the desert. This shows a logical order of discussing different animals.