First sentence: Why this is the first line? This paragraph is the first sentence because it introduces the main topic of origami. It uses the rule of Topic Sentence because it talks about origami and what is needed to start. It does not refer to any previous information. Why other lines are not chosen? The other paragraphs are not chosen because they do not meet the criteria for being independent. For example, Paragraph 2 starts with 'The initial step', which refers back to something not mentioned before. Paragraph 3 starts with 'Subsequently', which shows it is not independent. Paragraph 4 starts with 'Once', which also shows it is not independent.

Concluding sentence: Why this is the last line? This paragraph is the last sentence because it wraps up the topic of origami by discussing advanced figures. It uses the Conclusive Words rule, as it shows the final step after mastering the basics.

Paragraph pairs:

• Pair 1 (Paragraph 1 → Paragraph 2): Paragraph 2 connects with Paragraph 1 because it follows the topic of starting origami. It uses the Logical Order rule, as it explains the first step after selecting paper.
• Pair 2 (Paragraph 2 → Paragraph 3): Paragraph 3 connects with Paragraph 2 because it continues from learning basic folds to teaching specific folds. It uses the Broader to Specific Strategy, as it goes from general learning to specific types of folds.
• Pair 3 (Paragraph 3 → Paragraph 4): Paragraph 4 connects with Paragraph 3 because it talks about moving to advanced figures after learning the basic folds. It uses the Logical Order rule, as it shows the progression from basic to advanced.