Telephones are used for communication by two people by transmitting sound, and cell phones are, bottom line, radios with a connection to a telephone company. Given these facts, what are used for two people for communication with sound among the following options:
- cell phones
 - messengers
 - energy
 - megaphones
 - A Greek letter
 - flashlights
 - gramophones
 - electricity


 

 cell phones        