39174
Whereas standard US Army practice had been to seal , blow up or otherwise attempt to render tunnel systems unusable with smoke , tear gas and explosives before quickly moving on , MacGregor and his men searched and mapped the tunnels they found , using telephone line and compasses to plot the subterranean passages .
 None
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:  
Answer:
 None