A.I. Explanation:

First sentence: Why this is the first line? This paragraph is the first sentence because it introduces the main topic of seeking help for bed bug problems. It does not use any words that need prior context. It clearly states a situation and what the tenant can do. Why other lines are not chosen? Paragraph 2 starts with "Alternatively," which is a conjunction. Paragraph 3 starts with "Because," which shows a reason and needs more context. Paragraph 4 starts with "If," which also needs more context. All these reasons make them not independent.

Concluding sentence: Why this is the last line? This paragraph is the last sentence because it gives final advice on hiring an exterminator. It wraps up the discussion by showing what the tenant should do to ensure proper treatment.

Paragraph pairs:

• Pair 1 (Paragraph 1 → Paragraph 2): Paragraph 2 connects with Paragraph 1 because it offers another option for the tenant. The word "Alternatively" shows that this is a different choice after the first option.
• Pair 2 (Paragraph 2 → Paragraph 3): Paragraph 3 explains why hiring professionals is important. The word "Because" shows the reason for needing trained pest control, which follows the idea of hiring an exterminator.
• Pair 3 (Paragraph 3 → Paragraph 4): Paragraph 4 gives advice on what to do if the tenant hires an exterminator. It follows logically because it talks about the next steps after understanding the difficulty of bed bugs.