Electromagnetic waves are those waves that are composed of electric and magnetic fields perpendicular to each other and to the direction of the propagation. All electromagnetic waves have the same speed.
That is, 3×10⁸ m/s.
X-ray is one of the electromagnetic waves. So are light, gamma rays, and radio waves.
Thus the speed of all these waves is equal.
Thus, the correct answer is option C, "Same as speed of radio waves"
