675
Nearly one third of those surveyed had surgery at least once since retiring , mostly on knees with knee replacement a common option .
 person: Nearly one third of those surveyed; person: those surveyed
Please list all entity words in the text that fit the category.Output format is "type1: word1; type2: word2". 
Option: geographical social political, organization, person, location, facility, vehicle, weapon 
Text: {0} 
Answer:
 person: Nearly one third of those surveyed; person: those surveyed