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 the seeds of apple, cherry, and apricot and their natural toxins. This is a general statement that sets the stage for the following information. It does not use any pronouns or definite articles that would need prior context. Why other lines are not chosen? The other paragraphs are not chosen because they do not stand alone. For example, Paragraph 2 starts with "These seeds" which uses a pronoun that refers back to the seeds mentioned in Paragraph 1. Paragraph 3 starts with "The bitter flavor" which uses the definite article "the" and assumes prior knowledge. Paragraph 4 starts with "This substance" which also refers back to the toxins. Paragraph 5 starts with "The toxicity" which again uses a definite article and assumes prior context.

Concluding sentence: Why this is the last line? This paragraph is the last sentence because it wraps up the main idea of the text. It explains the reason for the toxicity of the seeds, which is to protect them from being eaten. This gives a clear conclusion to the information presented in the earlier paragraphs.

Paragraph pairs:

• Pair 1 (Paragraph 1 → Paragraph 2): Paragraph 2 connects with Paragraph 1 because it continues the topic of the seeds. The phrase "These seeds" refers back to the seeds mentioned in Paragraph 1. This shows a clear link between the two sentences.
• Pair 2 (Paragraph 2 → Paragraph 3): Paragraph 3 connects with Paragraph 2 because it explains why the seeds taste bitter. The word "bitter" is repeated, showing a clear connection between the two sentences.
• Pair 3 (Paragraph 3 → Paragraph 4): Paragraph 4 connects with Paragraph 3 because it gives more information about the compound amygdalin. The word "substance" refers back to amygdalin, showing a logical flow of ideas.
• Pair 4 (Paragraph 4 → Paragraph 5): Paragraph 5 connects with Paragraph 4 because it explains the purpose of the toxicity. The word "toxicity" refers back to the toxins mentioned earlier, showing a clear relationship between the two sentences.