Sarah and maria made a telephone using two cans and a string. it was a very long string. maria went upstairs in her house and sarah stayed downstairs. maria spoke softly into the can. "i can hear you! ' sarah said back. how can this happen? a)sound waves travel through a vacuum. b)sound waves travel from high to low. c)sound waves travel through solids like the string. eliminated)maria talked so loudly that sarah could hear her without the phone.