First sentence: Why this is the first line? This paragraph is the first because it introduces the main topic, which is the Alps. It gives a broad overview of what the text will discuss. It does not use any words that need prior context. Why other lines are not chosen? Paragraph 2 starts with 'This energy,' which needs context from earlier sentences. Paragraph 3 starts with 'The highest mountain range,' but it is not independent because it refers to the Alps. Paragraph 4 starts with 'Major road and rail routes,' which is not general and needs context. Paragraph 5 starts with 'Fast and efficient electric railways,' which also needs context.

Concluding sentence: Why this is the last line? This paragraph is the last because it wraps up the discussion about the Alps. It gives a final detail about the popularity of the railways, which connects back to the main topic of the Alps.

Paragraph pairs:

• Pair 1 (Paragraph 1 → Paragraph 2): This pair connects because Paragraph 2 explains what kind of engineering projects are in the Alps. It uses the 'Broader to Specific Strategy' because it goes from a general statement about the Alps to a specific example of hydroelectric power.
• Pair 2 (Paragraph 2 → Paragraph 3): This pair connects because Paragraph 3 explains why the energy from hydroelectric power is important. It uses the 'Cause and Effect Relationship' rule because the energy is a result of the dams mentioned in Paragraph 2.
• Pair 3 (Paragraph 3 → Paragraph 4): This pair connects because Paragraph 4 shows how the Alps are important for transport. It uses the 'Logical Order' rule because it moves from discussing energy to discussing transport routes.
• Pair 4 (Paragraph 4 → Paragraph 5): This pair connects because Paragraph 5 gives more details about the railways that use the routes mentioned in Paragraph 4. It uses the 'Topical Order' rule because both paragraphs discuss transport in the Alps.