While all waves can transmit energy through a medium, certain waves can also transmit energy through empty space. A medium is a material through which waves can travel. It can be a solid, liquid, or gas. When waves travel through a medium, the particles of the medium are not carried along with the wave.
Since energy can neither be created nor destroyed and it just changes from one form to another...so...
A.
Energy is neither lost nor gained as electrical energy is transformed into the energy of sound.
