7768
It continued to be the only type of radio transmission during the first few decades of radio , called the " wireless telegraphy era " up until World War I , when the development of amplitude modulation ( AM ) radiotelephony allowed sound ( audio ) to be transmitted by radio .
 event: World War I
Please list all entity words in the text that fit the category.Output format is "type1: word1; type2: word2". 
Option: media, plant, vehicle, astronomical object, time, disease, animal, location, person, organization, mythical figure, food, biology, geographical phenomenon, instrument, event 
Text: {0} 
Answer:
 event: World War I