First sentence: Why this is the first line? This paragraph is the first sentence because it introduces the main topic of the text, which is about researchers and their interest in games. It does not refer to any previous information. This follows the rule of Topic Sentence. Why other lines are not chosen? Paragraph 2 starts with "Games provide" which is not independent because it uses the definite article "the". Paragraph 3 starts with "Ever since" which is not independent because it refers to a specific event. Paragraph 4 starts with "Today, though" which is not independent because it uses a transitional phrase.

Concluding sentence: Why this is the last line? This paragraph is the last sentence because it wraps up the discussion about games and computers. It shows the current state of affairs and concludes the ideas presented in the previous paragraphs. 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 games. The first paragraph talks about researchers' interest in games, and the second paragraph explains why games are important. This follows the Broader to Specific Strategy.
• Pair 2 (Paragraph 2 → Paragraph 3): Paragraph 3 connects to Paragraph 2 because it gives a specific example of how games show the design of clever machines. The second paragraph talks about the design elements, and the third paragraph gives the example of Deep Blue. This follows the Topic Example Strategy.
• Pair 3 (Paragraph 3 → Paragraph 4): Paragraph 4 connects to Paragraph 3 because it shows the current situation of games and computers. The third paragraph talks about the past victory, and the fourth paragraph talks about the present actions. This follows the Chronological Order Strategy.