A.I. Explanation:

First sentence: Why this is the first line? This paragraph is the first sentence because it introduces the main topic of processed foods. It gives a broad overview of how common these foods are in diets. It does not use any words 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 "These foods," which refers back to processed foods, so it cannot be first. Paragraph 3 starts with "Additionally," which is a conjunction. Paragraph 4 starts with "However," which also is a conjunction. All these reasons make them not independent.

Concluding sentence: Why this is the last line? This paragraph is the last sentence because it wraps up the discussion about processed foods. It gives a conclusion about the risks of eating too many processed foods.

Paragraph pairs:

• Pair 1 (Paragraph 1 → Paragraph 2): Paragraph 2 connects with Paragraph 1 because it continues the topic of processed foods. The phrase "These foods" refers back to processed foods, showing a clear link.
• Pair 2 (Paragraph 2 → Paragraph 3): Paragraph 3 connects with Paragraph 2 because it adds more information about processed foods. The word "Additionally" shows that it is giving more details about the same topic.
• Pair 3 (Paragraph 3 → Paragraph 4): Paragraph 4 connects with Paragraph 3 because it introduces a contrast. The word "However" shows that it is talking about a different side of processed foods, which is the health risks.