A.I. Explanation:

First sentence: Why this is the first line? This paragraph is the first sentence because it introduces the main topic about O'Keeffe's theories on art. It does not refer to any previous information and stands alone. This follows the rule of Topic Sentence. Why other lines are not chosen? Paragraph 2 starts with 'She did,' which uses a pronoun and cannot stand alone. Paragraph 3 starts with 'Correspondence,' which is not a general statement. Paragraph 4 starts with 'The two exchanged,' which uses the definite article 'the' and assumes prior knowledge.

Concluding sentence: Why this is the last line? This paragraph is the last sentence because it summarizes the main points about O'Keeffe's letters and her development as an artist. It wraps up the discussion and provides a conclusion to the topic.

Paragraph pairs:

• Pair 1 (Paragraph 1 → Paragraph 2): Paragraph 2 connects to Paragraph 1 because it continues the idea of O'Keeffe's work. The phrase 'She did, however,' shows a contrast and links the two ideas. This follows the Connector Strategy.
• Pair 2 (Paragraph 2 → Paragraph 3): Paragraph 3 connects to Paragraph 2 because it gives an example of the letters mentioned in Paragraph 2. The word 'Correspondence' shows that it is related to the letters. This follows the Topic Example strategy.
• Pair 3 (Paragraph 3 → Paragraph 4): Paragraph 4 connects to Paragraph 3 because it gives more details about the correspondence mentioned. The phrase 'The two exchanged' continues the story of O'Keeffe and Stieglitz. This follows the Logical Order strategy.