A.I. Explanation:

First sentence: Why this is the first line? This paragraph is the first sentence because it introduces Karl Marx and his importance. It gives a broad overview of who he is without needing other sentences for context. It does not start with a conjunction or use pronouns that refer to other ideas. Why other lines are not chosen? Paragraph 2 starts with 'During' which is a conjunction. Paragraph 3 starts with 'Particularly' which is also a conjunction. Paragraph 4 starts with 'Above all' which is a transitional phrase. All these do not stand alone as independent sentences.

Concluding sentence: Why this is the last line? This paragraph is the last sentence because it wraps up the main ideas about Marx's work. It uses conclusive words like 'above all' to show it is a summary of his impact.

Paragraph pairs:

• Pair 1 (Paragraph 1 → Paragraph 2): Paragraph 2 connects to Paragraph 1 because it gives more details about Marx's work as a correspondent. This shows a logical order from introducing Marx to explaining what he did.
• Pair 2 (Paragraph 2 → Paragraph 3): Paragraph 3 connects to Paragraph 2 because it gives specific examples of the topics Marx wrote about. This shows a broader to specific strategy, moving from general topics to specific issues.
• Pair 3 (Paragraph 3 → Paragraph 4): Paragraph 4 connects to Paragraph 3 because it summarizes the impact of Marx's writing. It shows a logical order from discussing specific pieces to explaining their importance.