First sentence: Why this is the first line? This paragraph is the first sentence because it introduces the main topic of palm lines. It gives a clear 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, 'They form in the womb...' starts with a pronoun and needs context. 'These lines develop...' also uses a pronoun. 'However, the exact genetic...' starts with a conjunction, which means it cannot be first.

Concluding sentence: Why this is the last line? This paragraph is the last sentence because it wraps up the discussion. It shows that there is still more to learn about palm lines. It gives a conclusion to the information presented.

Paragraph pairs:

• Pair 1 (Paragraph 1 → Paragraph 2): Paragraph 2 connects to Paragraph 1 because it gives more information about palm lines. It explains when they start to form. This shows a logical order from a general statement to a specific detail.
• Pair 2 (Paragraph 2 → Paragraph 3): Paragraph 3 connects to Paragraph 2 because it explains how the lines develop. This shows a cause and effect relationship. The second paragraph talks about when they form, and the third explains how.
• Pair 3 (Paragraph 3 → Paragraph 4): Paragraph 4 connects to Paragraph 3 because it talks about what is not known about palm lines. It shows a logical order from explaining how they form to discussing the unknown factors.