A.I. Explanation:

First sentence: Why this is the first line? This paragraph is the first because it introduces the main topic about the Celts and their influence today. It gives a broad overview of who the Celts are and how they are still present in place names. This follows the rule of Topic Sentence. Why other lines are not chosen? Paragraph 2 starts with "The Celts' first homeland..." which refers to a specific idea and does not stand alone. Paragraph 3 starts with "They were warriors..." which uses a pronoun that refers back to the Celts. Paragraph 4 starts with "Their opponents..." which also uses a pronoun. Paragraph 5 starts with "In order to scare..." which is a specific action and does not introduce the topic.

Concluding sentence: Why this is the last line? This paragraph is the last because it describes the actions of the Celtic warriors in detail. It wraps up the discussion about the Celts by showing how they looked and acted in battle. This follows the Summary Style rule, as it brings together the earlier points about the Celts and their fearsome reputation.

Paragraph pairs:

• Pair 1 (Paragraph 1 → Paragraph 2): Paragraph 2 connects to Paragraph 1 because it gives more information about the Celts. This follows the Broader to Specific Strategy. The first paragraph talks about the Celts in general, and the second paragraph gives details about where they came from.
• Pair 2 (Paragraph 2 → Paragraph 3): Paragraph 3 connects to Paragraph 2 because it explains more about the Celts. This follows the Logical Order rule. After talking about their homeland, it makes sense to talk about what they did as warriors, farmers, and traders.
• Pair 3 (Paragraph 3 → Paragraph 4): Paragraph 4 connects to Paragraph 3 because it shows the effect of the Celtic warriors. This follows the Cause and Effect Relationship rule. The paragraph explains what the Celts did and then tells how their opponents felt about them.
• Pair 4 (Paragraph 4 → Paragraph 5): Paragraph 5 connects to Paragraph 4 because it explains why the Celtic warriors were terrifying. This follows the Logical Order rule. The fourth paragraph talks about the fear they caused, and the fifth paragraph describes their actions that created that fear.