All of the following are electromagnetic waves except

a. X rays.

b. sound waves.

c. gamma rays.

d. radio waves.

B. sound waves

Sound waves need to travel through a medium such as a solid, liquid, or gas. The sound waves move through each of these mediums by vibrating the molecules in the matter. This means it isn't an electromagnetic waves but it is a wave, an example of the difference, all electromagnetic waves can travel in a vacuum at the universal speed limit, this is 299 792 458 m/s.