45646
The marshlands were an extensive natural wetlands ecosystem which developed over thousands of years in the Tigris–Euphrates basin and once covered 15 – 20,000 square kilometers .
 location: Tigris–Euphrates
Given options, please tell me the categories of all the listed entity words.Output format is "type1: word1; type2: word2". 
Option: location, person, organization 
Text: {0} 
 Entities: Tigris–Euphrates 
Answer:
 location: Tigris–Euphrates