Which of the following statements about electromagnetic radiation is true? A) It always travels at 3Ã108 m/s.
B) It consists of perpendicularly oscillating electric and magnetic fields, and the direction of propagation is perpendicular to both.
C) It consists of oscillating electric and magnetic fields that are parallel to one another and perpendicular to the direction of propagation.
D) The oscillating electric and magnetic fields are completely out of phase with one another

The correct option is B: It consists of perpendicularly oscillating electric and magnetic fields, and the direction of propagation is perpendicular to both.

Explanation:

Electromagnetic radiation travels at the speed of light (c = 3x10⁸ m/s) only in a vacuum. In another propagation medium, the speed of electromagnetic radiation is less than c.    

The oscillations of the waves of the electric and magnetic fields are perpendicular to each other, and the direction of propagation is also perpendicular to the two fields.        

From all of the above, the correct option is B: It consists of perpendicularly oscillating electric and magnetic fields, and the direction of propagation is perpendicular to both.        

I hope it helps you!