A.I. Explanation:

First sentence: Why this is the first line? This paragraph is the first sentence because it introduces the main topic. It shows the main idea about humans and melodies. It does not need other sentences to understand it. It does not start with a conjunction or use pronouns. It uses an indefinite article to introduce a general idea. Why other lines are not chosen? Paragraph 2 starts with "It was thought" which makes it dependent. Paragraph 3 starts with "To test this theory" which needs context. Paragraph 4 starts with "As in previous studies" which refers back to earlier information.

Concluding sentence: Why this is the last line? This paragraph is the last sentence because it wraps up the main idea. It summarizes the findings and connects back to the previous studies. It uses conclusive words to show that it is the end of the discussion.

Paragraph pairs:

• Pair 1 (Paragraph 1 → Paragraph 2): Paragraph 2 connects with Paragraph 1 because it explains why humans cannot recognize melodies. It uses the Connector strategy to show the relationship between the studies and the thought about soundwaves.
• Pair 2 (Paragraph 2 → Paragraph 3): Paragraph 3 connects with Paragraph 2 because it shows the next step after the thought about soundwaves. It uses the Logical Order strategy to show how the idea of testing the theory follows the explanation.
• Pair 3 (Paragraph 3 → Paragraph 4): Paragraph 4 connects with Paragraph 3 because it gives the result of the test. It uses the Cause and Effect Relationship strategy to show that the test results support the earlier studies.