First sentence: Why this is the first line? This paragraph is the first sentence because it introduces the main topic of reproduction in sharks. It gives a broad overview of the subject without going into details. 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 'Some sharks lay eggs,' which needs context. Paragraph 3 starts with 'Moreover,' which is a conjunction. Paragraph 4 uses 'This,' which refers back to something else.

Concluding sentence: Why this is the last line? This paragraph is the last sentence because it wraps up the discussion about shark reproduction. It shows the consequence of the slow reproductive process, which is a clear conclusion.

Paragraph pairs:

• Pair 1 (Paragraph 1 → Paragraph 2): Paragraph 2 connects to Paragraph 1 because it gives specific examples of how reproduction varies. This follows the Broader to Specific Strategy.
• Pair 2 (Paragraph 2 → Paragraph 3): Paragraph 3 connects to Paragraph 2 because it adds more information about the reproductive rates of sharks. This follows the Logical Order rule.
• Pair 3 (Paragraph 3 → Paragraph 4): Paragraph 4 connects to Paragraph 3 because it explains the effect of low reproductive rates. This follows the Cause and Effect Relationship rule.