A.I. Explanation:

First sentence: Why this is the first line? This paragraph is the first sentence because it introduces the main topic of the text. It tells us what the study is about. It does not refer to any previous information. This follows the rule of Topic Sentence. Why other lines are not chosen? Paragraph 2 starts with "At first," which is a transitional phrase. This means it connects to something before it, so it cannot be the first. Paragraph 3 starts with "As the semester progressed," which also shows a time connection. Paragraph 4 starts with "This trend," which refers back to something mentioned before. 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 main idea of the text. It gives a conclusion about the study's findings. This follows the Conclusive Words rule.

Paragraph pairs:

• Pair 1 (Paragraph 1 → Paragraph 2): Paragraph 2 connects to Paragraph 1 because it continues the idea of the study. It shows what happened at the start of the study. This follows the Logical Order rule.
• Pair 2 (Paragraph 2 → Paragraph 3): Paragraph 3 connects to Paragraph 2 because it shows what happened later in the study. It explains how the performance changed over time. This follows the Chronological Order rule.
• Pair 3 (Paragraph 3 → Paragraph 4): Paragraph 4 connects to Paragraph 3 because it explains the result of the findings. It shows what the higher scores mean. This follows the Cause and Effect Relationship rule.