A.I. Explanation:

First sentence: Why this is the first line? This paragraph is the first sentence because it gives a broad overview of the population. It does not need another sentence for context. It introduces the main topic of urban population. This follows the rule of Topic Sentence. Why other lines are not chosen? The other paragraphs are not chosen because they do not meet the criteria for being independent. For example, Paragraph 2 starts with 'The estimated', which uses the definite article 'the' and assumes prior knowledge. Paragraph 3 starts with 'The density', which also uses 'the'. Paragraph 4 starts with 'The population', which again uses 'the'. Paragraph 5 starts with 'In the rural areas', which is not general and assumes context.

Concluding sentence: Why this is the last line? This paragraph is the last sentence because it provides a conclusion about the rural population. It wraps up the discussion about the population by showing a different aspect of it. This follows the Summary Style rule.

Paragraph pairs:

• Pair 1 (Paragraph 1 → Paragraph 2): Paragraph 2 connects with Paragraph 1 because it continues the topic of population. It uses the Logical Order rule, as it gives more specific information about the population after stating the urban percentage.
• Pair 2 (Paragraph 2 → Paragraph 3): Paragraph 3 connects with Paragraph 2 because it elaborates on the density mentioned in Paragraph 2. This follows the Broader to Specific Strategy, as it gives more details about the density.
• Pair 3 (Paragraph 3 → Paragraph 4): Paragraph 4 connects with Paragraph 3 because it provides a specific number for the population. This follows the Logical Order rule, as it gives a clear fact after discussing density.
• Pair 4 (Paragraph 4 → Paragraph 5): Paragraph 5 connects with Paragraph 4 because it shifts focus to rural areas. This follows the Same Theme rule, as it discusses different aspects of the population.