1. An extensive area of flat or rolling, predominantly treeless grassland, especially the large tract or plain of central North America. 
   大草原多为广阔而无树木的平坦或起伏的草原区域，尤指北美洲中部的大平原
2. diseases of biliary tract 
   胆道系统疾病
3. diverticulum of digestive tract 
   消化道憩室
4. hernia of digestive tract 
   消化道疝
5. recanalization of reproductive tract 
   复孕术

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