35581
Cervical mucus is used in several methods of fertility awareness , such as the Creighton model and Billings method , due to its changes in consistency throughout the menstrual period .
 person: Creighton; person: Billings
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: Creighton, Billings 
Answer:
 person: Creighton; person: Billings