A.I. Explanation:

First sentence: Why this is the first line? This paragraph is the first sentence because it introduces the main topic of blockchain technology. It gives a broad overview of what blockchain is about without going into details. This follows the rule of Topic Sentence. Why other lines are not chosen? Paragraph 2 starts with "Originally" which shows it is not independent. Paragraph 3 starts with "Yet" which is a conjunction. Paragraph 4 starts with "As a result" which is also a conjunction. All these sentences need context from previous sentences.

Concluding sentence: Why this is the last line? This paragraph is the last sentence because it wraps up the discussion about blockchain technology. It shows what developers are doing to solve the challenges. This follows the Conclusive Words strategy.

Paragraph pairs:

• Pair 1 (Paragraph 1 → Paragraph 2): Paragraph 2 connects to Paragraph 1 because it gives more details about blockchain technology. It explains where blockchain started and how it is used in different areas. This follows the Broader to Specific Strategy.
• Pair 2 (Paragraph 2 → Paragraph 3): Paragraph 3 connects to Paragraph 2 because it talks about the challenges of blockchain technology. After explaining its uses, it is logical to mention the problems. This follows the Logical Order strategy.
• Pair 3 (Paragraph 3 → Paragraph 4): Paragraph 4 connects to Paragraph 3 because it shows what is being done about the challenges mentioned. It explains the response to the problems. This follows the Cause and Effect Relationship strategy.