challenge: What are the four major types of habitat within the Charles M. Russell National Wildlife Refuge?
  
  A. River bottom, riparian zones and wetlands, shoreline, and mountainous regions
  B. River bottom, riparian zones and wetlands, shoreline, and desert regions
  C. River bottom, riparian zones, and wetlands, upland, and tundra
  D. River bottom, riparian zones and wetlands, shoreline, and upland
  Answer: 