Modal dispersion is caused by the
∙ a. Dependence of wavelength on index of refraction
∙ b. Dependence of propagation constant on index of refraction
∙ c. Dependence of the propagation constant on the wavelength
∙ d. Dependence of the propagation constant on the mode number
∙ a. Dependence of wavelength on index of refraction
∙ b. Dependence of propagation constant on index of refraction
∙ c. Dependence of the propagation constant on the wavelength
∙ d. Dependence of the propagation constant on the mode number