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 and its dangers. It is a clear statement that does not need other sentences for context. It sets the stage for the discussion about diabetes. Why other lines are not chosen? The other paragraphs are not chosen because they do not stand alone. For example, Paragraph 2 starts with 'But,' which is a conjunction. Paragraph 3 and Paragraph 4 both refer to treatment, which needs the context of the problem first.

Concluding sentence: Why this is the last line? This paragraph is the last sentence because it gives the final details about treatment options for diabetes. It wraps up the discussion by explaining what treatments can be used after talking about diet.

Paragraph pairs:

• Pair 1 (Paragraph 1 → Paragraph 2): Paragraph 2 connects with Paragraph 1 because it uses the connector 'But,' which shows a contrast between the danger of untreated diabetes and the possibility of a normal life with treatment.
• Pair 2 (Paragraph 2 → Paragraph 3): Paragraph 3 logically follows Paragraph 2 because it gives a specific example of what treatment can be. It goes from a general statement about treatment to a specific type of treatment.
• Pair 3 (Paragraph 3 → Paragraph 4): Paragraph 4 connects with Paragraph 3 because it continues the topic of treatment. It provides more details about the types of treatment after mentioning diet.