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, which is the migration of the monarch butterfly. It does not refer to any previous information and gives a broad overview of the subject. Why other lines are not chosen? Paragraph 2 starts with 'This journey,' which refers back to the migration mentioned in Paragraph 1, so it cannot be first. Paragraph 3 starts with 'However,' which shows a contrast and cannot be first. Paragraph 4 starts with 'As a result,' which indicates it is a conclusion and cannot be first.

Concluding sentence: Why this is the last line? This paragraph is the last sentence because it summarizes the main points of the text. It shows the outcome of the issues discussed earlier and reflects the overall theme of concern for the monarch butterfly's future.

Paragraph pairs:

• Pair 1 (Paragraph 1 → Paragraph 2): Paragraph 2 connects to Paragraph 1 because it explains more about the journey of the monarch butterfly. This shows a logical order where the first paragraph introduces the topic and the second gives more details about it.
• Pair 2 (Paragraph 2 → Paragraph 3): Paragraph 3 connects to Paragraph 2 because it introduces a problem that affects the butterflies' journey. The word 'However' shows a contrast between the remarkable journey and the challenges they face.
• Pair 3 (Paragraph 3 → Paragraph 4): Paragraph 4 connects to Paragraph 3 because it explains the result of the problems mentioned in Paragraph 3. The phrase 'As a result' shows that the decline in milkweed leads to a reduction in the butterfly population.