First sentence: Why this is the first line? This paragraph is the first line because it introduces the main topic about food in schools. It does not need other sentences for context. It talks about a general problem without specific details. This follows the rule of Topic Sentence. Why other lines are not chosen? Paragraph 2 starts with 'Teenage boys' which is specific and needs context. Paragraph 3 starts with 'Exercise' which also needs context. Paragraph 4 uses 'It is estimated' which is not independent because it refers to a specific number. All these sentences do not stand alone.

Concluding sentence: Why this is the last line? This paragraph is the last line because it summarizes the problem of obesity. It gives a final number and shows the seriousness of the issue. This follows the Summary Style rule.

Paragraph pairs:

• Pair 1 (Paragraph 1 → Paragraph 2): Paragraph 2 connects to Paragraph 1 because it continues the topic of food. The drinks mentioned in Paragraph 2 relate to the food problem in schools. This follows the Logical Order rule.
• Pair 2 (Paragraph 2 → Paragraph 3): Paragraph 3 connects to Paragraph 2 because it talks about exercise and obesity, which are related to the drinks in Paragraph 2. This shows a Cause and Effect Relationship.
• Pair 3 (Paragraph 3 → Paragraph 4): Paragraph 4 connects to Paragraph 3 because it talks about obesity, which is the result of the lack of exercise mentioned in Paragraph 3. This follows the Cause and Effect Relationship.