A.I. Explanation:

First sentence: Why this is the first line? This paragraph is the first sentence because it introduces the main topic of who can issue currency. It uses a broad overview to set the stage for the discussion. It does not refer to any previous information, making it independent. 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 'But', which is a conjunction. Paragraph 3 uses 'The first Scottish bank', which assumes prior knowledge. Paragraph 4 starts with 'When', indicating a time context that requires prior information. Paragraph 5 starts with 'To face', which suggests a purpose that needs context.

Concluding sentence: Why this is the last line? This paragraph is the last sentence because it summarizes the need for the bank and the currency issue. It wraps up the discussion by showing the result of the previous points.

Paragraph pairs:

• Pair 1 (Paragraph 1 → Paragraph 2): Paragraph 2 connects with Paragraph 1 using the Connector strategy. The word 'But' shows a contrast between the general rule in most countries and the special case in Scotland.
• Pair 2 (Paragraph 2 → Paragraph 3): Paragraph 3 follows Paragraph 2 logically because it uses the Object Subject Strategy. The subject of Paragraph 2 is the banks in Scotland, and Paragraph 3 talks about the first bank, which continues the topic.
• Pair 3 (Paragraph 3 → Paragraph 4): Paragraph 4 connects with Paragraph 3 using the Logical Order strategy. It gives background information about the Bank of Scotland, explaining why it was needed.
• Pair 4 (Paragraph 4 → Paragraph 5): Paragraph 5 follows Paragraph 4 using the Cause and Effect Relationship strategy. It explains the need for the bank due to the problems mentioned in Paragraph 4.