First sentence: Why this is the first line? This paragraph is the first line because it introduces the main ideas of dependence and rivalry between painting and photography. It gives a broad overview of their relationship without going into specific 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 'Photography,' which needs context from the first sentence. Paragraph 3 starts with 'Yet,' which shows it is continuing a thought. Paragraph 4 starts with 'How,' which also needs prior information to make sense.

Concluding sentence: Why this is the last line? This paragraph is the last line because it wraps up the discussion about painting and photography. It introduces the exhibition that explores their relationship, which follows the Summary Style rule. It brings together the earlier points about their rivalry and influence.

Paragraph pairs:

• Pair 1 (Paragraph 1 → Paragraph 2): Paragraph 2 connects to Paragraph 1 because it continues the idea of photography's relationship with painting. This follows the Logical Order rule, as it explains how photography looked to painting after discussing their rivalry.
• Pair 2 (Paragraph 2 → Paragraph 3): Paragraph 3 connects to Paragraph 2 because it shows the effect of photography on painting. The word 'Yet' indicates a contrast, which follows the Contrast rule. It explains how photography changed the role of painting.
• Pair 3 (Paragraph 3 → Paragraph 4): Paragraph 4 connects to Paragraph 3 because it discusses the ongoing relationship between painting and photography. It provides a broader context for their rivalry, following the Broader to Specific Strategy.