A.I. Explanation:

First sentence: Why this is the first line? This paragraph is the first sentence because it introduces the main topic. It gives a clear starting point about when the company began its work. It does not need any other sentence for context. This follows the rule of Topic Sentence. Why other lines are not chosen? The other paragraphs are not chosen because they do not stand alone. For example, Paragraph 2 starts with 'The company', which needs context. Paragraph 3 starts with 'Initially', which shows it is not the first. Paragraph 4 starts with 'Four deep shafts', which also needs prior information. All these reasons make them not independent.

Concluding sentence: Why this is the last line? This paragraph is the last sentence because it wraps up the information. It gives a final detail about the work done by the company. It does not need any more information after it. This follows the rule of Topic Closure.

Paragraph pairs:

• Pair 1 (Paragraph 1 → Paragraph 2): Paragraph 2 connects with Paragraph 1 because it continues the story of the company. The phrase 'The company' refers back to the Mendip Hills Mining Company. This follows the Noun Pronoun Rule.
• Pair 2 (Paragraph 2 → Paragraph 3): Paragraph 3 connects with Paragraph 2 because it explains why the company employed the miners. The word 'Initially' shows that this is the first aim of the company. This follows the Logical Order rule.
• Pair 3 (Paragraph 3 → Paragraph 4): Paragraph 4 connects with Paragraph 3 because it gives details about how the aim was achieved. The phrase 'Four deep shafts' shows the action taken to reach the ore. This follows the Broader to Specific Strategy.