Fact 1: Telephones are used for communication by two people by transmitting sound.

Fact 2: Sound waves are longitudinal waves.

Given the two facts above, answer the question "What are used for communication by two people by transmitting waves?" with the following options: 
- satellites
 - A Greek letter
 - Morse code
 - mitosis
 - telephones
 - energy
 - electricity
 - photosynthesis


 

     telephones    