Electromagnetic waves have the following characteristics:
• Travel in vacuum: They do not require a medium for propagation, unlike mechanical waves, such as sound.
• Transverse waves: Electromagnetic waves are characterized by oscillating electric and magnetic fields which are perpendicular to each other and also to the direction of wave propagation.
• Include X-rays and gamma rays: X-rays are a high-energy form of electromagnetic radiation, along with gamma rays, visible light, UV and radio waves
• Not sound waves: sound waves are mechanical waves and require medium for propagation. They are also longitudinal waves.
Therefore, statements B and D are correct, while statements A and C are incorrect.