First sentence: Why this is the first line? This paragraph is the first line because it gives a clear overview of the main topic. It introduces the idea of population growth without needing other sentences for context. It does not use any pronouns or definite articles that refer to previous ideas. Why other lines are not chosen? Paragraph 2 starts with 'But', which is a conjunction and does not stand alone. Paragraph 3 uses 'We’ll likely have', which is not general and needs context. Paragraph 4 uses 'If these trends continue', which also needs prior information to understand.

Concluding sentence: Why this is the last line? This paragraph is the last line because it wraps up the discussion. It gives a conclusion about the future need for food based on the trends mentioned before.

Paragraph pairs:

• Pair 1 (Paragraph 1 → Paragraph 2): Paragraph 2 connects to Paragraph 1 because it adds more information about the need for food. The word 'But' shows a contrast to the idea of just population growth.
• Pair 2 (Paragraph 2 → Paragraph 3): Paragraph 3 explains another reason for needing more food. It continues the thought from Paragraph 2 by showing that there are more factors, like prosperity, that increase food demand.
• Pair 3 (Paragraph 3 → Paragraph 4): Paragraph 4 follows logically because it shows the result of the trends mentioned in Paragraph 3. It explains what will happen if the demand for food continues to grow.