A.I. Explanation:

First sentence: Why this is the first line? This paragraph is the first sentence because it introduces the main topic of digital marketing. It clearly states what digital marketing is and sets the stage for the following information. 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 "Its" which is a pronoun and needs context. Paragraph 3 starts with "Digital marketing extends" which is not a general statement. Paragraph 4 starts with "The extension" which uses a definite article and assumes prior knowledge.

Concluding sentence: Why this is the last line? This paragraph is the last sentence because it wraps up the discussion by explaining a key difference in digital marketing. It uses conclusive words by showing how digital marketing is different from online advertising.

Paragraph pairs:

• Pair 1 (Paragraph 1 → Paragraph 2): Paragraph 2 connects to Paragraph 1 because it explains how digital marketing has changed over time. This follows the Logical Order rule, as it shows the development of the topic introduced in Paragraph 1.
• Pair 2 (Paragraph 2 → Paragraph 3): Paragraph 3 connects to Paragraph 2 because it shows how digital marketing includes more than just online methods. This follows the Broader to Specific Strategy, as it expands on the topic of digital marketing.
• Pair 3 (Paragraph 3 → Paragraph 4): Paragraph 4 connects to Paragraph 3 because it explains why the inclusion of non-internet channels is important. This follows the Cause and Effect Relationship rule, as it shows the result of the extension mentioned in Paragraph 3.