First sentence: Why this is the first line? This paragraph is the first sentence because it introduces the main topic of the text. It is a clear statement about the invention of the airplane. It does not need any other sentence for context. 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 "Initially," which is a conjunction. Paragraph 3 starts with "Over time," which also shows a sequence. Paragraph 4 starts with "Consequently," which is another conjunction. These words show that they need more context to make sense.

Concluding sentence: Why this is the last line? This paragraph is the last sentence because it wraps up the main ideas of the text. It shows the result of the improvements in airplane technology. This follows the Conclusive Words rule, as it uses "Consequently" to show the outcome of earlier points.

Paragraph pairs:

• Pair 1 (Paragraph 1 → Paragraph 2): Paragraph 2 connects with Paragraph 1 because it gives more details about the early airplanes. This follows the Broader to Specific Strategy. The first sentence talks about the invention, and the second sentence explains what those early airplanes were like.
• Pair 2 (Paragraph 2 → Paragraph 3): Paragraph 3 connects with Paragraph 2 because it shows how airplanes improved over time. This follows the Logical Order rule. The second sentence talks about early airplanes, and the third sentence explains how they became better.
• Pair 3 (Paragraph 3 → Paragraph 4): Paragraph 4 connects with Paragraph 3 because it shows the result of the advancements mentioned in the third sentence. This follows the Cause and Effect Relationship rule. The third sentence talks about improvements, and the fourth sentence explains what those improvements mean for today's airplanes.