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U. S. Comptroller General David M. Walker was an advisor and participated in each of the Tour 's public events .
 person: David M. Walker
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: David M. Walker 
Answer:
 person: David M. Walker