A.I. Explanation:

First sentence: Why this is the first line? This paragraph is the first line because it introduces the main topic. It tells us who is doing the research and what the research is about. This follows the rule of Topic Sentence. Why other lines are not chosen? The other paragraphs are not chosen because they do not stand alone. For example, Paragraph 2 starts with 'He' which is a pronoun. This means it needs more context. Paragraph 3 uses 'this' which also needs prior information. Paragraph 4 starts with 'So' which is a conjunction. Paragraph 5 starts with 'He' too, which is not independent.

Concluding sentence: Why this is the last line? This paragraph is the last line because it wraps up the findings of Dr Pitsiladis's research. It gives a final result of his study. This follows the Conclusive Words rule.

Paragraph pairs:

• Pair 1 (Paragraph 1 → Paragraph 2): Paragraph 2 connects to Paragraph 1 because it continues the story of Dr Pitsiladis's research. This follows the Logical Order rule.
• Pair 2 (Paragraph 2 → Paragraph 3): Paragraph 3 connects to Paragraph 2 because it shows the result of the DNA testing. This follows the Cause and Effect Relationship rule.
• Pair 3 (Paragraph 3 → Paragraph 4): Paragraph 4 connects to Paragraph 3 because it shows what Dr Pitsiladis did next after his conclusion. This follows the Logical Order rule.
• Pair 4 (Paragraph 4 → Paragraph 5): Paragraph 5 connects to Paragraph 4 because it gives more details about the children he studied. This follows the Broader to Specific Strategy.