1521
( voice - over ) : But among the boats , guns , radar , sonar and communications , we found a secret weapon posted on the side of the tent that serves as the command center : letters from second - graders .
 we, second - graders, the tent that serves as the command center, that, the command center, the boats , guns , radar , sonar and communications
Please list all entity words in the text that fit the category. Output format is "word1, word2". 
Option: organization, person, geographical social political, vehicle, location, weapon, facility 
Text: {0} 
Answer:
 we, second - graders, the tent that serves as the command center, that, the command center, the boats , guns , radar , sonar and communications