A.I. Explanation:

First sentence: Why this is the first line? This paragraph is the first sentence because it introduces a new topic about a Mongolian horse. It does not refer to any previous information. It gives a broad overview of the subject. Why other lines are not choosen? The other paragraphs are not chosen because they do not stand alone. For example, Paragraph 2 starts with "It turns out" which needs context. Paragraph 3 starts with "What’s more" which is a conjunction. Paragraph 4 starts with "These are" which refers back to something not yet mentioned. Paragraph 5 starts with "That means" which also needs prior context.

Concluding sentence: Why this is the last line? This paragraph is the last sentence because it wraps up the discussion about horses. It gives a conclusion about the findings of the study. It reflects the overarching theme of the text.

Paragraph pairs:

• Pair 1 (Paragraph 1 → Paragraph 2): Paragraph 2 connects to Paragraph 1 because it explains what the horses are. This follows the Broader to Specific Strategy. The first paragraph talks about a Mongolian horse, and the second paragraph gives more details about its background.
• Pair 2 (Paragraph 2 → Paragraph 3): Paragraph 3 connects to Paragraph 2 because it adds more information about modern horses. This follows the Logical Order rule. The second paragraph talks about feral horses, and the third paragraph shows how they relate to modern horses.
• Pair 3 (Paragraph 3 → Paragraph 4): Paragraph 4 connects to Paragraph 3 because it explains the conclusions of the study about horses. This follows the Cause and Effect Relationship rule. The third paragraph states a fact, and the fourth paragraph explains the study that supports this fact.
• Pair 4 (Paragraph 4 → Paragraph 5): Paragraph 5 connects to Paragraph 4 because it explains the implications of the study. This follows the Topic Example rule. The fourth paragraph presents findings, and the fifth paragraph shows what those findings mean for the history of horse domestication.