A.I. Explanation:

First sentence: Why this is the first line? This paragraph is the first sentence because it introduces the main topic of diabetes. It gives a broad overview of what diabetes is without going into details. This follows the rule of Topic Sentence. Why other lines are not chosen? Paragraph 2 starts with "This problem" which refers back to something, so it is not independent. Paragraph 3 starts with "If diabetes is untreated" which is a conditional phrase, so it is not independent. Paragraph 4 starts with "Uncontrolled changes" which also does not stand alone without context, so it is not independent.

Concluding sentence: Why this is the last line? This paragraph is the last sentence because it summarizes the effects of diabetes. It gives a clear conclusion about what can happen if diabetes is not managed. This follows the Summary Style rule.

Paragraph pairs:

• Pair 1 (Paragraph 1 → Paragraph 2): Paragraph 2 connects to Paragraph 1 because it explains the problem of diabetes. This follows the Logical Order rule, as it gives more detail about the cause of diabetes.
• Pair 2 (Paragraph 2 → Paragraph 3): Paragraph 3 connects to Paragraph 2 because it shows the result of the problem explained in Paragraph 2. This follows the Cause and Effect Relationship rule, as it explains what happens if diabetes is not treated.
• Pair 3 (Paragraph 3 → Paragraph 4): Paragraph 4 connects to Paragraph 3 because it gives specific effects of untreated diabetes. This follows the Broader to Specific Strategy, as it goes from a general statement about danger to specific symptoms.