31998
From 28 March to 11 April 1939 , the prototype was studied by NACA .
 organization: NACA
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: NACA 
Answer:
 organization: NACA