A.I. Explanation:

First sentence: Why this is the first line? This paragraph is the first sentence because it introduces the main topic of cultural anthropology. It gives a broad overview of its history and does not need any other sentence for context. It does not use any pronouns or definite articles that refer to previous ideas. Why other lines are not chosen? Paragraph 2 starts with 'They', which is a pronoun and needs context. Paragraph 3 also starts with 'They', which makes it dependent on previous sentences. Paragraph 4 starts with 'This', which refers back to something not yet mentioned. All these reasons make them not independent.

Concluding sentence: Why this is the last line? This paragraph is the last sentence because it wraps up the discussion. It gives the final reason for the dismissal of the scholars. It summarizes the main points and reflects the overall theme of the text.

Paragraph pairs:

• Pair 1 (Paragraph 1 → Paragraph 2): Paragraph 2 connects to Paragraph 1 because it continues the topic of cultural anthropology. It explains how early scholars used Darwin's theories. This shows a logical order from the introduction of the topic to a specific example.
• Pair 2 (Paragraph 2 → Paragraph 3): Paragraph 3 follows Paragraph 2 because it explains the outcome of the ideas from Paragraph 2. It shows a cause and effect relationship. The scholars used Darwin's ideas, but later they were dismissed.
• Pair 3 (Paragraph 3 → Paragraph 4): Paragraph 4 connects to Paragraph 3 because it gives the reason why they were called 'armchair anthropologists'. It uses a cause and effect relationship. The dismissal is explained by their lack of personal engagement.