Waves is the disturbance that propagate energy through the medium. So here if we will say that sound waves are produced then in that case we need some disturbance which will carry the sound energy through the medium.
Here this disturbance is created by the vibration of medium particles so in order to produce sound we need to vibrate the medium.
Due to the vibration of medium it will transfer energy to the air particles and then due to this vibration of air molecules this is transferred to the receiver of the sound energy
The answer is D) vibrate. vibrations are what cause sound. Consequently, this is why there is no sound in space, because there is no medium for the for which sound to travel
