A.I. Explanation:

First sentence: Why this is the first line? This paragraph is the first sentence because it introduces the main topic. It tells us what Washington DC is and its importance as the capital of the United States. This follows the rule of Topic Sentence. Why other lines are not chosen? Paragraph 2 starts with 'It has', which is a pronoun and does not stand alone. Paragraph 3 starts with 'Popular', which is not a general statement. Paragraph 4 starts with 'It has', which is also a pronoun. Paragraph 5 starts with 'President', which is specific and assumes prior knowledge.

Concluding sentence: Why this is the last line? This paragraph is the last sentence because it wraps up the information about the White House. It gives a historical fact that concludes the discussion about the White House. This follows the Conclusive Words rule.

Paragraph pairs:

• Pair 1 (Paragraph 1 → Paragraph 2): The second paragraph connects to the first because it gives more information about Washington DC. It explains the population of the city, which is related to its status as the capital. This follows the Logical Order rule.
• Pair 2 (Paragraph 2 → Paragraph 3): The third paragraph connects to the second because it shifts from population to tourism. It shows what people can see in Washington, which is related to the number of commuters. This follows the Broader to Specific Strategy.
• Pair 3 (Paragraph 3 → Paragraph 4): The fourth paragraph connects to the third because it gives specific details about the White House, which is mentioned in the third paragraph. This follows the Topic Example rule.
• Pair 4 (Paragraph 4 → Paragraph 5): The fifth paragraph connects to the fourth because it continues to talk about the White House. It gives historical information about the White House after mentioning its rooms. This follows the Same Theme rule.