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So ever since the Middle Ages , when the process of land reclamation began , different societies living in the same polder have been forced to cooperate because without unanimous agreement on shared responsibility for maintenance of the dykes and pumping stations , the polders would have flooded and everyone would have suffered .
 time: Middle Ages
Given options, please tell me the categories of all the listed entity words.Output format is "type1: word1; type2: word2". 
Option: media, plant, vehicle, astronomical object, time, disease, animal, location, person, organization, mythical figure, food, biology, geographical phenomenon, instrument, event 
Text: {0} 
 Entities: Middle Ages 
Answer:
 time: Middle Ages