Radish Pork Ribs Soup

Ingredients: 
A rack of pork ribs, radish, green onion.

Steps:
1. Cut the ribs, radish and green onion into pieces.
2. Heat a pot of water until boil. Add ribs, cook for 1 minute. Remove and drain them.
3. Put cold water into a pot. Add ribs, radish. Medium heat until boil. 
4. Cover with lid. Low heat for 3 hours or more.
5. Add green onion before serve.