Radio waves are not mechanical waves.
Mechanical waves are waves that require a physical medium, such as a solid, liquid, or gas, to travel through. They transfer energy through the vibration of particles in the medium.
On the other hand, radio waves are a type of electromagnetic wave, which means they do not require a physical medium to travel through. They can travel through a vacuum, such as space, and are created by the acceleration of electric charges. Radio waves are used for communication, including radio and television broadcasting, as well as cellular and satellite communication.
Therefore, the answer is option (iii) radio waves.