First sentence: Why this is the first line? This paragraph is the first line because it introduces the main topic of world maps. 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? The other paragraphs are not chosen because they do not stand alone. For example, Paragraph 2 starts with "However," which is a conjunction. Paragraph 3 uses "they" which refers back to world maps, so it cannot be independent. Paragraph 4 starts with "This limitation," which also needs prior context.

Concluding sentence: Why this is the last line? This paragraph is the last line because it wraps up the discussion. It summarizes the main point about the difficulty of showing the Earth's geography accurately. It gives a clear conclusion to the text.

Paragraph pairs:

• Pair 1 (Paragraph 1 → Paragraph 2): Paragraph 2 connects to Paragraph 1 because it continues the topic of world maps. It explains that there are different types of maps. This shows a logical order from a general statement to more specific details.
• Pair 2 (Paragraph 2 → Paragraph 3): Paragraph 3 connects to Paragraph 2 because it introduces a problem with maps. The word "However" shows a contrast to the information about different types of maps. This is a cause and effect relationship.
• Pair 3 (Paragraph 3 → Paragraph 4): Paragraph 4 connects to Paragraph 3 because it explains the limitation mentioned in Paragraph 3. The phrase "This limitation" refers back to the distortion, showing a clear link between the two.