A.I. Explanation:

First sentence: Why this is the first line? This paragraph is the first sentence because it introduces the main topic of the text. It talks about the CPU unit and its relation to the microprocessor. This is an introductory statement that sets the stage for the following information. It does not refer to any previous information, so it stands alone. Why other lines are not chosen? The other paragraphs are not chosen as the first sentence because they do not meet the criteria for being independent. For example, Paragraph 2 starts with 'The microprocessor', which refers back to the topic introduced in Paragraph 1. Paragraph 3 also starts with 'In many computers', which is too specific and assumes prior knowledge. Paragraph 4 starts with 'However', which is a conjunction and shows a continuation of thought.

Concluding sentence: Why this is the last line? This paragraph is the last sentence because it wraps up the discussion about the microprocessor's speed and power. It provides a final thought that connects back to the earlier points made in the text. It does not introduce new ideas but summarizes the conditions affecting the microprocessor.

Paragraph pairs:

• Pair 1 (Paragraph 1 → Paragraph 2): Paragraph 2 connects with Paragraph 1 because it explains what the microprocessor does. This is a logical order where the first paragraph introduces the microprocessor, and the second paragraph describes its function. This follows the Logical Order rule.
• Pair 2 (Paragraph 2 → Paragraph 3): Paragraph 3 connects with Paragraph 2 because it gives more details about the microprocessor's speed. This shows a Broader to Specific Strategy, where the second paragraph gives a general idea, and the third paragraph provides specific information about its speed.
• Pair 3 (Paragraph 3 → Paragraph 4): Paragraph 4 connects with Paragraph 3 because it adds a condition about the microprocessor's speed. It shows a Cause and Effect Relationship, where the speed mentioned in the third paragraph is affected by the factors discussed in the fourth paragraph.