A.I. Explanation:

First sentence: Why this is the first line? This paragraph is the first sentence because it introduces the main topic. It tells us about the commission given to Picasso. It does not need any other sentence to understand it. It does not start with a conjunction or use pronouns. It sets the stage for the rest of the text. Why other lines are not chosen? Paragraph 2 starts with "He" which is a pronoun, so it cannot be independent. Paragraph 3 starts with "He" too, which makes it dependent. Paragraph 4 starts with "On the first of May" which is a specific time reference, so it cannot be independent either.

Concluding sentence: Why this is the last line? This paragraph is the last sentence because it wraps up the story about Picasso. It shows what he did after the commission. It gives a clear end to the topic of his work on the painting Guernica.

Paragraph pairs:

• Pair 1 (Paragraph 1 → Paragraph 2): Paragraph 2 connects to Paragraph 1 because it gives more information about Picasso. It shows where he was living at that time. This is a logical order because it continues the story about Picasso.
• Pair 2 (Paragraph 2 → Paragraph 3): Paragraph 3 connects to Paragraph 2 because it explains that even though Picasso was in Paris, he still had ties to Spain. The word "however" shows a contrast between his situation in Paris and his connections to Spain.
• Pair 3 (Paragraph 3 → Paragraph 4): Paragraph 4 connects to Paragraph 3 because it shows what Picasso did after agreeing to the commission. It continues the story of Picasso's work and gives a specific event that happened next.