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The Apache troop opened its tank guns , opened its own mortars , decimated that unit , put it out of existence and probably killed some 20 Iraqis in the process .
 troop: attacker; unit: target; guns: instrument
Given event type and trigger, please tell me the arguments of all the listed option. Output format is "name1: role1; name2: role2". 
Event type: attack 
  Option: victim, attacker, place, target, instrument 
Text: {0} 
Answer:
 troop: attacker; unit: target; guns: instrument