Explanation:

- Raman Effect: ?? This option is correct. When light passes through a medium, a small fraction is scattered. This scattered light can undergo a change in wavelength due to energy being transferred to or from vibrational energy levels of the molecules.

- Rayleigh Effect: It involves the scattering of light by particles much smaller than the wavelength of light, without any change in wavelength. It explains why the sky is blue.

- Huygens Effect: Not a commonly recognized term related to light scattering. Huygens is known for the Huygens' Principle related to wave propagation.

- Maxwell Effect: More associated with electromagnetic theory, not specifically with vibrational energy levels or light scattering.