Explanation: The wavelength of a radio wave is the distance it travels during one complete cycle. To calculate this, we use the fundamental relationship: Wavelength ($\lambda$) = Speed of Light (c) $\times$ Period (T). The speed of light (c) in a vacuum is approximately 300,000,000 meters per second (or 3 x 10$^8$ m/s). The given period (T) is 0.000,001 seconds, which can also be written as 1 x 10$^{-6}$ seconds. Plugging these values into the formula: $\lambda$ = 300,000,000 m/s $\times$ 0.000,001 s $\lambda$ = 300 meters Therefore, the wavelength is 300 M. Options B, C, and D are incorrect because they result from miscalculations or using different values for the period or speed of light.