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 tells us that the researchers are setting up an experiment. This is an overview of what the text will discuss. It does not refer to any previous information, so it stands alone. Why other lines are not chosen? Paragraph 2 starts with "Before they started the experiment," which refers back to the experiment mentioned in Paragraph 1. Paragraph 3 starts with "In the training," which also refers back to the experiment. Paragraph 4 starts with "The hole at one end," which needs context from earlier sentences. Paragraph 5 starts with "The calves learned quickly," which also needs context from previous sentences.

Concluding sentence: Why this is the last line? This paragraph is the last sentence because it concludes the text. It summarizes the main result of the experiment. It shows what the calves learned from the training and the setup.

Paragraph pairs:

• Pair 1 (Paragraph 1 → Paragraph 2): Paragraph 2 connects to Paragraph 1 because it explains what happened before the experiment. The phrase "Before they started the experiment" shows a logical order of events.
• Pair 2 (Paragraph 2 → Paragraph 3): Paragraph 3 connects to Paragraph 2 because it describes the training mentioned in Paragraph 2. The phrase "In the training" shows that this is a specific detail about the training process.
• Pair 3 (Paragraph 3 → Paragraph 4): Paragraph 4 connects to Paragraph 3 because it gives more details about the holes in the pen. The phrase "The hole at one end" continues the description of the setup in the training.
• Pair 4 (Paragraph 4 → Paragraph 5): Paragraph 5 connects to Paragraph 4 because it shows the result of the setup. The phrase "The calves learned quickly" indicates the outcome of the experiment.