A.I. Explanation:

First sentence: Why this is the first line? This paragraph is the first sentence because it introduces the main topic about computers and their hard drive space. It gives a broad overview without going into details. 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 'However,' which is a conjunction. Paragraph 3 starts with 'There are,' which is not general. Paragraph 4 uses 'One option,' which needs context. Paragraph 5 starts with 'Another,' which also needs context.

Concluding sentence: Why this is the last line? This paragraph is the last sentence because it adds a final option to the solutions for the problem. It wraps up the discussion about ways to address the issue of hard drive space.

Paragraph pairs:

• Pair 1 (Paragraph 1 → Paragraph 2): Paragraph 2 connects to Paragraph 1 because it uses the connector 'However.' This shows a contrast between having space and the problem of filling it up. This follows the Contrast rule.
• Pair 2 (Paragraph 2 → Paragraph 3): Paragraph 3 connects to Paragraph 2 because it follows the logical order of discussing the problem and then stating that there are ways to fix it. This follows the Logical Order rule.
• Pair 3 (Paragraph 3 → Paragraph 4): Paragraph 4 connects to Paragraph 3 because it gives a specific example of a way to address the problem mentioned in Paragraph 3. This follows the Broader to Specific Strategy.
• Pair 4 (Paragraph 4 → Paragraph 5): Paragraph 5 connects to Paragraph 4 because it gives another option after stating one. This follows the Logical Order rule.