12- Men who have walked on the moon

11- US States that seceded from the Union 

10- Ten Kingdoms of China

9- Little Rock Nine

8- Warsaw Pact countries

7- Sites of the Ancient Wonders of the World

6- Nobel Prize categories

5- Countries liberated by Simón Bolívar

4- “Big Four” leaders at post-WW1 Paris conference

3- Christopher Columbus’ ships

2- Peoples whose conflict led to the Rwandan genocide

1- Mongol emperor