First sentence: Why this is the first line? This paragraph is the first line because it introduces the main topic about the moon's impact before artificial light. It does not refer to any previous information, so it is independent. 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 'And,' which is a conjunction. Paragraph 3 uses 'Hence,' which also shows it is not independent. Paragraph 4 starts with 'In,' which is not a strong start for a first sentence.

Concluding sentence: Why this is the last line? This paragraph is the last line because it wraps up the discussion about the moon and solar year. It provides a conclusion about how the solar year is important in northern areas. This follows the Conclusive Words rule.

Paragraph pairs:

• Pair 1 (Paragraph 1 → Paragraph 2): Paragraph 2 connects to Paragraph 1 because it continues the idea of the moon's influence. The phrase 'And, for those living near the equator' shows a logical flow from the general impact of the moon to a specific group of people. This follows the Logical Order rule.
• Pair 2 (Paragraph 2 → Paragraph 3): Paragraph 3 connects to Paragraph 2 because it explains the effect of the moon's visibility on calendars. The word 'Hence' shows a cause and effect relationship, linking the conspicuousness of the moon to the development of calendars. This follows the Cause and Effect Relationship rule.
• Pair 3 (Paragraph 3 → Paragraph 4): Paragraph 4 connects to Paragraph 3 because it contrasts the lunar influence with the solar year in northern areas. The word 'however' shows a contrast between the two ideas. This follows the Contrast rule.