A.I. Explanation:

First sentence: Why this is the first line? This paragraph is the first sentence because it introduces the main topic of formal vocabulary. It does not need another sentence for context. It is a general statement that sets up the discussion without specifics. Why other lines are not chosen? The other paragraphs are not chosen because they do not meet the criteria for being independent. For example, Paragraph 2 starts with 'This can mean,' which is not independent. Paragraph 3 starts with 'A passage with a lot of these words,' which refers back to the topic of vocabulary. Paragraph 4 starts with 'For example,' which shows it is not independent. Paragraph 5 starts with 'This example,' which also refers back to something else.

Concluding sentence: Why this is the last line? This paragraph is the last sentence because it summarizes the main idea of the previous paragraphs. It wraps up the discussion about formal vocabulary and its academic tone.

Paragraph pairs:

• Pair 1 (Paragraph 1 → Paragraph 2): This pair connects because Paragraph 2 explains what is meant by formal vocabulary. It uses the 'Broader to Specific Strategy' where the first sentence gives a general idea and the second gives specific examples.
• Pair 2 (Paragraph 2 → Paragraph 3): This pair connects because Paragraph 3 describes the effect of using formal vocabulary. It follows a 'Logical Order' where the explanation of vocabulary leads to the result of having a formal tone.
• Pair 3 (Paragraph 3 → Paragraph 4): This pair connects because Paragraph 4 gives an example of how formal vocabulary can be used. It uses the 'Topic Example' strategy where the example follows the statement about formal tone.
• Pair 4 (Paragraph 4 → Paragraph 5): This pair connects because Paragraph 5 summarizes the example given in Paragraph 4. It uses the 'Conclusive Words' strategy where the last sentence wraps up the example.