A.I. Explanation:

First sentence: Why this is the first line? This paragraph is the first sentence because it introduces the main idea of the text. It gives a broad overview of the importance of a healthy school setting. It does not refer to any previous information. Why other lines are not chosen? Paragraph 2 starts with "Vaccines are very important..." which is not a general statement. Paragraph 3 starts with "They protect..." which uses a pronoun that refers back to something not yet mentioned. Paragraph 4 starts with "For this reason..." which shows it is connected to something before it.

Concluding sentence: Why this is the last line? This paragraph is the last sentence because it wraps up the text. It gives a clear action that is taken based on the importance of vaccines. It shows the conclusion of the ideas presented.

Paragraph pairs:

• Pair 1 (Paragraph 1 → Paragraph 2): Paragraph 2 connects to Paragraph 1 because it explains why a healthy school setting is important. It shows that vaccines help create this healthy setting. This is a logical order.
• Pair 2 (Paragraph 2 → Paragraph 3): Paragraph 3 connects to Paragraph 2 because it explains how vaccines help. It shows the effect of vaccines, which is to protect children from diseases.
• Pair 3 (Paragraph 3 → Paragraph 4): Paragraph 4 connects to Paragraph 3 because it explains what is done to protect children. It shows the action taken because of the protection vaccines provide.