First sentence: Why this is the first line? This paragraph is the first sentence because it introduces the main topic. It gives a broad overview of the robots and where they are. It does not need any other sentence for context. It does not use any pronouns or definite articles that refer to previous information. Why other lines are not chosen? Paragraph 2 starts with "One underwater robot" which uses a determiner that suggests prior knowledge. Paragraph 3 starts with "The drone" which also uses a definite article. Paragraph 4 starts with "Litter collection" which is not general. Paragraph 5 starts with "Equipped with a gripper" which is specific and does not stand alone.

Concluding sentence: Why this is the last line? This paragraph is the last sentence because it wraps up the information about the robots. It explains how the second robot works and gives a complete picture of the topic.

Paragraph pairs:

• Pair 1 (Paragraph 1 → Paragraph 2): This pair connects because Paragraph 2 explains what one of the robots does. It follows the topic introduced in Paragraph 1. This is a logical order.
• Pair 2 (Paragraph 2 → Paragraph 3): This pair connects because Paragraph 3 introduces another robot, the drone. It adds more information about how garbage is found. This shows a broader to specific strategy.
• Pair 3 (Paragraph 3 → Paragraph 4): This pair connects because Paragraph 4 talks about the second robot that collects litter. It follows the information about the drone and continues the topic of robots.
• Pair 4 (Paragraph 4 → Paragraph 5): This pair connects because Paragraph 5 gives details about how the second robot collects waste. It explains the process after introducing the robot.