Final answer:
An electromagnetic wave is produced by oscillating charges, specifically oscillations of electric and magnetic fields. These oscillations create a transverse wave.
Step-by-step explanation:
An electromagnetic wave is produced by oscillating charges. The type of oscillation that would most likely produce an electromagnetic wave is an oscillation of electric and magnetic fields. The electric and magnetic fields in electromagnetic waves are perpendicular to the direction in which the wave moves, making it a transverse wave.