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Anthropologist David Graeber has argued that for most of human history , money has been widely understood to represent debt , though he concedes that even prior to the modern era , there have been several periods where rival theories like metallism have held sway .
 person: David Graeber; time: modern era
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: David Graeber, modern era 
Answer:
 person: David Graeber; time: modern era