First sentence: Why this is the first line? This paragraph is the first sentence because it introduces the main topic of the experiment. It does not need another sentence for context. It is a general statement about the experiment. Why other lines are not chosen? Paragraph 2 starts with 'In this experiment,' which refers back to the experiment, so it is not independent. Paragraph 3 starts with 'Initially,' which suggests it is part of a sequence, so it is not independent. Paragraph 4 starts with 'After one week,' which also suggests a sequence, so it is not independent.

Concluding sentence: Why this is the last line? This paragraph is the last sentence because it wraps up the findings of the experiment. It summarizes the results and shows the conclusion about the interactive method.

Paragraph pairs:

• Pair 1 (Paragraph 1 → Paragraph 2): This pair connects because Paragraph 2 explains what happened in the experiment mentioned in Paragraph 1. It follows the 'Broader to Specific Strategy' as it gives more details about the experiment.
• Pair 2 (Paragraph 2 → Paragraph 3): This pair connects because Paragraph 3 describes the results of the teaching methods mentioned in Paragraph 2. It follows the 'Logical Order' as it shows what happened after the teaching.
• Pair 3 (Paragraph 3 → Paragraph 4): This pair connects because Paragraph 4 explains the results after a week, showing a change in retention rates. It follows the 'Cause and Effect Relationship' as it shows the effect of time on retention.