A.I. Explanation:

First sentence: Why this is the first line? This paragraph is the first sentence because it introduces the main topic of advertisers and their thinking. It does not need another sentence for context. It sets up the main idea without going into details. Why other lines are not chosen? The other paragraphs are not chosen because they do not stand alone. For example, Paragraph 2 starts with 'Their critics', which needs context from a previous sentence. Paragraph 3 uses 'they say', which also needs prior information. Paragraph 4 starts with 'It only goes to show', which refers back to something earlier.

Concluding sentence: Why this is the last line? This paragraph is the last sentence because it wraps up the discussion. It gives a conclusion about the profit of big companies and asks a question that reflects the main theme.

Paragraph pairs:

• Pair 1 (Paragraph 1 → Paragraph 2): This pair connects because Paragraph 2 explains why advertisers get criticism. The phrase 'because they have' shows a cause and effect relationship.
• Pair 2 (Paragraph 2 → Paragraph 3): This pair connects because Paragraph 3 gives a strong opinion about the advertising industry. The phrase 'they say' shows that it is a response to the critics mentioned in Paragraph 2.
• Pair 3 (Paragraph 3 → Paragraph 4): This pair connects because Paragraph 4 explains the result of the situation in Paragraph 3. The phrase 'It only goes to show' shows a logical order from the problem to the conclusion.