The way to separate colors is by using a prism (option A). A prism works by refracting white light, which consists of all visible wavelengths, into its individual components—colors of the rainbow. Each color bends differently due to its specific wavelength, resulting in a spectrum ranging from red to violet. This phenomenon is known as dispersion. By observing the light that emerges from the prism, one can clearly distinguish and study the different colors present in white light. This method of separating colors has been instrumental in understanding the properties of light and color, including the principles of wavelength, frequency, and the behavior of light in different media. Unlike options B and C, which are unrelated to the physics of light and color separation, and option D, which is incorrect as colors can indeed be separated by various means, using a prism remains a fundamental and effective method for studying the nature and characteristics of light.