A.I. Explanation:

First sentence: Why this is the first line? This paragraph is the first line because it introduces the main topic of segregation in education. It does not need another sentence for context. It sets up the theme of the text without going into details. This follows the rule of Topic Sentence. Why other lines are not chosen? Paragraph 2 starts with 'The end of legal segregation...' which refers back to the previous context, so it is not independent. Paragraph 3 starts with 'On every major national test...' which is specific and assumes prior knowledge. Paragraph 4 starts with 'On the Scholastic Aptitude Test...' which also assumes prior knowledge. All these reasons make them not independent.

Concluding sentence: Why this is the last line? This paragraph concludes the text by providing a specific example of the changes in test scores. It wraps up the discussion about educational achievement and segregation. This follows the Conclusive Words rule.

Paragraph pairs:

• Pair 1 (Paragraph 1 → Paragraph 2): Paragraph 2 connects with Paragraph 1 because it shows the result of the situation described in Paragraph 1. This follows the Cause and Effect Relationship rule.
• Pair 2 (Paragraph 2 → Paragraph 3): Paragraph 3 continues the idea from Paragraph 2 by showing how the end of segregation affected test scores. This follows the Logical Order rule.
• Pair 3 (Paragraph 3 → Paragraph 4): Paragraph 4 provides a specific example of the trend mentioned in Paragraph 3. This follows the Broader to Specific Strategy.