A.I. Explanation:

First sentence: Why this is the first line? This paragraph is the first sentence because it introduces the main topic. It talks about the sounds of rushing water in Idaho's Pioneer Mountains. This sets the scene without needing any prior context. It gives a broad overview of the environment. Why other lines are not chosen? The other paragraphs are not chosen because they do not stand alone. For example, Paragraph 2 starts with 'But,' which is a conjunction. Paragraph 3 uses 'These,' which refers back to something not yet mentioned. Paragraph 4 starts with 'He,' which is a pronoun. Paragraph 5 starts with 'There’s,' which does not introduce a new idea.

Concluding sentence: Why this is the last line? This paragraph is the last sentence because it summarizes the main points. It wraps up the discussion about the effects of noise on animals. It gives a clear conclusion to the topic.

Paragraph pairs:

• Pair 1 (Paragraph 1 → Paragraph 2): Paragraph 2 connects to Paragraph 1 because it uses the word 'But.' This shows a contrast between loud sounds and gentle streams. It helps to continue the idea of sound in nature.
• Pair 2 (Paragraph 2 → Paragraph 3): Paragraph 3 connects to Paragraph 2 because it talks about 'These phantom rivers.' This refers back to the sounds mentioned in Paragraph 2. It shows a logical order from the sounds to the experiment.
• Pair 3 (Paragraph 3 → Paragraph 4): Paragraph 4 connects to Paragraph 3 because it explains what the experiment was about. It continues the topic of the experiment and shows the logical order of testing a hypothesis.
• Pair 4 (Paragraph 4 → Paragraph 5): Paragraph 5 connects to Paragraph 4 because it provides more information about the effects of noise on animals. It shows a cause and effect relationship, where the hypothesis leads to research findings.