First sentence: Why this is the first line? This paragraph is the first sentence because it introduces the main topic of the text. It clearly states what plate tectonics is and its importance in geology. 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 'The Earth's surface', which uses a definite article and refers to a specific subject. Paragraph 3 starts with 'This has led', which refers back to something not yet mentioned. Paragraph 4 starts with 'These plates', which also refers back to a subject not yet introduced.

Concluding sentence: Why this is the last line? This paragraph is the last sentence because it wraps up the explanation of plate tectonics. It gives the final detail about how the plates move, which is important to understand the whole topic. This follows the Conclusive Words rule.

Paragraph pairs:

• Pair 1 (Paragraph 1 → Paragraph 2): Paragraph 2 connects with Paragraph 1 because it continues the explanation of plate tectonics. It uses the Logical Order rule, as it describes what plate tectonics involves.
• Pair 2 (Paragraph 2 → Paragraph 3): Paragraph 3 connects with Paragraph 2 because it explains the results of the plates being divided. This follows the Cause and Effect Relationship rule, as it shows what happens because of the plates.
• Pair 3 (Paragraph 3 → Paragraph 4): Paragraph 4 connects with Paragraph 3 because it explains how the plates move. This follows the Broader to Specific Strategy, as it gives more detail about the movement of the plates.