1. "Why do cats chase mice?"
  2. "Where do birds migrate in winter?"
  3. "When does the library close?"
  4. "What foods contain the most vitamins?"
  5. "How do people celebrate New Year's Eve around the world?"
  6. "Who writes the laws in a country?"
  7. "Which planet is closest to the sun?"
  8. "Whose painting sold for the highest price at auction?"
  9. "What time does the sunrise in Tokyo?"
  10. "Why do leaves change color in autumn?"
  11. "How many languages are spoken in India?"
  12. "Where do most people live in the world?"
  13. "When do students graduate from high school in the United States?"
  14. "What causes thunder and lightning?"
  15. "How do birds know where to migrate?"
  16. "Who discovered penicillin?"
  17. "Which movie won the Best Picture Oscar last year?"
  18. "Whose theory of relativity changed physics?"
  19. "What kind of gas do cars emit?"
  20. "Why do people dream?"