A.I. Explanation:

First sentence: Why this is the first line? This paragraph is the first sentence because it introduces the main topic of climate change and its impact on crops. It is a general statement that does not need other sentences for context. It sets the stage for the discussion. Why other lines are not chosen? The other paragraphs are not chosen because they do not stand alone. For example, Paragraph 2 starts with 'For example,' which is a conjunction. Paragraph 3 starts with 'Consequently,' which also shows a connection to previous ideas. Paragraph 4 starts with 'However,' which indicates a contrast and needs prior context.

Concluding sentence: Why this is the last line? This paragraph is the last sentence because it wraps up the discussion by highlighting the challenges of the solutions. It reflects on the main theme of the text, which is about climate change and crop cultivation.

Paragraph pairs:

• Pair 1 (Paragraph 1 → Paragraph 2): Paragraph 2 connects to Paragraph 1 because it gives specific examples of how climate change affects crops. This follows the 'Broader to Specific Strategy' where the first sentence is general and the second gives details.
• Pair 2 (Paragraph 2 → Paragraph 3): Paragraph 3 connects to Paragraph 2 because it shows the result of the problems mentioned. The word 'Consequently' indicates a cause and effect relationship, showing that the challenges lead to a focus on solutions.
• Pair 3 (Paragraph 3 → Paragraph 4): Paragraph 4 connects to Paragraph 3 because it discusses the challenges of implementing the solutions mentioned. The word 'However' shows a contrast, indicating that while there is a focus on solutions, there are still difficulties.