First sentence: Why this is the first line? This paragraph is the first sentence because it introduces the main topic of the text. It defines what a zombie computer is without needing other sentences for context. This follows the rule of Topic Sentence. Why other lines are not choosen? The other paragraphs are not chosen because they do not stand alone. For example, Paragraph 2 starts with 'Groups of such machines', which needs context from a previous sentence. Paragraph 3 starts with 'Over timer', which does not introduce a new idea. Paragraph 4 starts with 'The only cure', which assumes knowledge of the topic.

Concluding sentence: Why this is the last line? This paragraph is the last sentence because it gives a solution to the problem discussed in the text. It wraps up the ideas about zombie computers and their effects, following the Summary Style rule.

Paragraph pairs:

• Pair 1 (Paragraph 1 → Paragraph 2): Paragraph 2 connects to Paragraph 1 because it explains what happens to zombie computers. This follows the Logical Order rule, as it continues the idea of zombie computers by introducing botnets.
• Pair 2 (Paragraph 2 → Paragraph 3): Paragraph 3 connects to Paragraph 2 because it shows the increase in zombie computers. This follows the Cause and Effect Relationship rule, as it explains the result of botnets.
• Pair 3 (Paragraph 3 → Paragraph 4): Paragraph 4 connects to Paragraph 3 because it talks about what to do with infected machines. This follows the Logical Order rule, as it provides a solution after discussing the problem.