Concept:All electromagnetic waves in a vacuum share the same speed.
Explanation:In a vacuum, every electromagnetic wave travels at the speed of light,
c=3×108 m/s.
This speed is constant for all electromagnetic waves.
It does not depend on wavelength, frequency, or amplitude.
Different electromagnetic waves have different wavelengths and frequencies, but their vacuum speed is always the same.
Hence, the property that is identical for all of them is speed.
Answer:C. speed