First sentence: Why this is the first line? This paragraph is the first sentence because it introduces the main topic of self-driving cars. It does not need other sentences for context. It is a general statement about Google and its work on self-driving cars. This follows the rule of Topic Sentence. Why other lines are not chosen? The other paragraphs are not chosen because: 1) "In 2012 they announced..." starts with a pronoun and needs context. 2) "That same year, Nevada..." refers to a specific year and needs prior information. 3) "Other states have taken no action yet." is a statement that does not introduce the topic.

Concluding sentence: Why this is the last line? This paragraph is the last sentence because it wraps up the discussion about self-driving cars. It shows that while some states are moving forward, others are not. This follows the Conclusive Words rule, as it gives a final thought on the topic.

Paragraph pairs:

• Pair 1 (Paragraph 1 → Paragraph 2): Paragraph 2 connects to Paragraph 1 because it gives specific information about Google's self-driving car. This follows the Broader to Specific Strategy. The first paragraph is general, and the second gives details about their announcement.
• Pair 2 (Paragraph 2 → Paragraph 3): Paragraph 3 connects to Paragraph 2 because it talks about the same year as the announcement. This follows the Chronological Order rule. It shows what happened in the same time frame.
• Pair 3 (Paragraph 3 → Paragraph 4): Paragraph 4 connects to Paragraph 3 because it shows a contrast. Nevada took action, but other states did not. This follows the Contrast rule.