A.I. Explanation:

First sentence: Why this is the first line? This paragraph is the first sentence because it introduces the main topic of food and sugar in the body. It gives a broad overview of what happens to food. It does not use any pronouns or definite articles that need prior context. Why other lines are not chosen? The other paragraphs are not chosen because they do not stand alone. For example, Paragraph 2 starts with 'When', which is a conjunction. Paragraph 3 uses 'When there isn’t enough insulin', which also starts with a conjunction. Paragraph 4 starts with 'Over time', which is not independent. Paragraph 5 starts with 'There isn’t a cure yet', which is not general enough to be the first sentence.

Concluding sentence: Why this is the last line? This paragraph is the last sentence because it wraps up the discussion about diabetes. It gives a conclusion about what can help with diabetes. It uses the phrase 'but' to show a contrast, which indicates it is the final thought.

Paragraph pairs:

• Pair 1 (Paragraph 1 → Paragraph 2): Paragraph 2 connects with Paragraph 1 because it continues the idea of sugar in the bloodstream. The phrase 'When your blood sugar goes up' shows a cause and effect relationship. It explains what happens after food is broken down.
• Pair 2 (Paragraph 2 → Paragraph 3): Paragraph 3 connects with Paragraph 2 because it talks about what happens when there is not enough insulin. The use of 'When' shows a logical order of events related to insulin and blood sugar.
• Pair 3 (Paragraph 3 → Paragraph 4): Paragraph 4 connects with Paragraph 3 because it explains the result of having too much blood sugar. The phrase 'Over time' shows the cause and effect relationship between high blood sugar and health problems.
• Pair 4 (Paragraph 4 → Paragraph 5): Paragraph 5 connects with Paragraph 4 because it talks about diabetes, which is mentioned in the previous paragraph. It provides a solution to the problem of diabetes, showing a logical order from problem to solution.