Answer the following question given this paragraph: 

Most ocean waves are caused by winds. A wave is the transfer of energy through matter. A wave that travels across miles of ocean is traveling energy, not water. Ocean waves transfer energy from wind to the water. The energy is transferred from one water molecule to the next. The energy of a wave may travel for thousands of miles. The water itself moves very little. The picture below shows how water molecules move when a wave goes by ( Figure below ). Once the wave starts, it doesn't need more wind to keep it going.


Q: A wave is the transfer of energy through what else?

 Choices:

- liquid

- air

- gas

- matter

A:
matter
