First sentence: Why this is the first line? This paragraph is the first sentence because it introduces the main topic of the text. It talks about the boom in general aviation after World War II. This is a broad overview of the subject. It does not use any pronouns or definite articles that refer to previous information. Why other lines are not chosen? Paragraph 2 starts with "Manufacturers" which is not independent because it needs context. Paragraph 3 starts with "By the 1950s" which is not independent because it refers to a time without context. Paragraph 4 starts with "At the same time" which is not independent because it connects to previous ideas.

Concluding sentence: Why this is the last line? This paragraph is the last sentence because it wraps up the discussion about aviation developments. It shows how turboprop propulsion was important for smaller planes. This gives a complete view of the topic.

Paragraph pairs:

• Pair 1 (Paragraph 1 → Paragraph 2): Paragraph 2 connects to Paragraph 1 because it continues the topic of general aviation. The sentence shows how manufacturers responded to the boom in aviation. This is a logical order of ideas.
• Pair 2 (Paragraph 2 → Paragraph 3): Paragraph 3 connects to Paragraph 2 because it shows the next step in aviation development. After light aircraft, the text talks about the growth of civil jets. This is a logical order of ideas.
• Pair 3 (Paragraph 3 → Paragraph 4): Paragraph 4 connects to Paragraph 3 because it talks about another development in aviation. It shows how turboprop propulsion was also important during the same time as civil jets. This is a logical order of ideas.