PLEASE ANSWE

Mrs. Smith wants her class to give her differences between light and sound waves. The class makes this list:

Electromagnetic waves need a medium, but mechanical waves do not.
Light travels faster in air than in water.
Sound travels faster in solids than in air.
Electromagnetic waves are transverse waves, but sound waves are longitudinal.
What error did the class make on their list?

A. Light waves do not require a medium to travel.
B. Light waves do not change speed when they change mediums.
C. Sound waves travel fastest in air.
D. Some sound waves are also transverse.