41520
Surrounding the city , Rock Bridge Memorial State Park , Mark Twain National Forest , and Big Muddy National Fish and Wildlife Refuge form a greenbelt preserving sensitive and rare environments .
 Rock Bridge Memorial State Park, Mark Twain National Forest, Big Muddy National Fish and Wildlife Refuge
Please list all entity words in the text that fit the category. Output format is "word1, word2". 
Option: location, person, organization 
Text: {0} 
Answer:
 Rock Bridge Memorial State Park, Mark Twain National Forest, Big Muddy National Fish and Wildlife Refuge