Question

what do all electromagnetic waves have in common?
they can travel at the speed of light.
they have the same wavelengths.
they travel only through matter.
they have nonmoving magnetic fields.

Explanation:

Electromagnetic waves can travel at the speed of light in a vacuum. Different electromagnetic waves have different wavelengths. They can travel through a vacuum (not only through matter). Electromagnetic waves have oscillating (not non - moving) electric and magnetic fields.

Answer:

They can travel at the speed of light.