A.I. Explanation:

First sentence: Why this is the first line? This paragraph is the first sentence because it introduces the main topic. It talks about reasons for not living healthily. This is an overview of the subject. It does not use any words that need prior context. Why other lines are not chosen? Paragraph 2 starts with 'Perhaps', which is a conjunction. Paragraph 3 starts with 'These include', which refers back to previous ideas. Paragraph 4 starts with 'Changing', which is not general and assumes prior knowledge.

Concluding sentence: Why this is the last line? This paragraph is the last sentence because it wraps up the main ideas. It talks about the challenge of changing behaviour and how the strategies help. It gives a conclusion to the discussion.

Paragraph pairs:

• Pair 1 (Paragraph 1 → Paragraph 2): This pair connects because the second paragraph builds on the first. The first talks about reasons for not living healthily, and the second gives a solution from behavioural science. This shows a logical order.
• Pair 2 (Paragraph 2 → Paragraph 3): This pair connects because the third paragraph gives specific examples of the strategies mentioned in the second paragraph. This is a broader to specific strategy.
• Pair 3 (Paragraph 3 → Paragraph 4): This pair connects because the fourth paragraph summarizes the importance of the strategies mentioned in the third paragraph. It shows the effect of using these strategies.