First sentence: Why this is the first line? This paragraph is the first sentence because it introduces the main topic of potential energy. It clearly states what potential energy is without needing other sentences for context. This follows the rule of Topic Sentence. Why other lines are not chosen? Paragraph 2 starts with "For example," which means it needs more context. Paragraph 3 starts with "When she is closest," which also needs context. Paragraph 4 starts with "Another example," needing prior information. Paragraph 5 starts with "At the highest point," which also needs context.

Concluding sentence: Why this is the last line? This paragraph is the last sentence because it wraps up the discussion about potential energy. It gives a final point about how potential energy changes, which follows the Conclusive Words rule.

Paragraph pairs:

• Pair 1 (Paragraph 1 → Paragraph 2): Paragraph 2 connects with Paragraph 1 because it gives an example of potential energy. This follows the Broader to Specific Strategy, where the first paragraph gives a general idea and the second gives a specific example.
• Pair 2 (Paragraph 2 → Paragraph 3): Paragraph 3 connects with Paragraph 2 because it shows another situation about potential energy. This follows the Logical Order rule, as it continues the discussion about potential energy in different positions.
• Pair 3 (Paragraph 3 → Paragraph 4): Paragraph 4 connects with Paragraph 3 because it gives another example of potential energy. This follows the Broader to Specific Strategy, as it continues to explain the topic with a new example.
• Pair 4 (Paragraph 4 → Paragraph 5): Paragraph 5 connects with Paragraph 4 because it explains the example of throwing a ball. This follows the Cause and Effect Relationship, as it shows what happens to potential energy when the ball is at its highest point.