Zeeman and Stark effects can be explained by _________________.
A. Principal Quantum Number
B. Azimuthal Quantum Number
C. Magnetic Quantum Number
D. Spin Quantum Number

Hint: The otherwise degenerate energy levels of the orbital can split up under the influence of magnetic and electric fields. The effect mentioned can be explained by the quantum number which specifies the orientation in space of an orbital of a given energy.

Complete Step by step Solution:
When an external magnetic or electric field is present the emission lines from different atoms and ions are split into several components. The magnitude of the wavelength separation and the relative intensity of the split line depend on the strength of the magnetic field. Such phenomenons caused by the magnetic and electric fields are called the Zeeman Effect and the Stark effect respectively. The splitting of these emission lines is ascribed to the resolutions of the magnetic sublevels that are otherwise degenerate under normal conditions.
The variation in the relative intensity of the lines is interpreted as a change of the electric dipole moment between the magnetic subshells of the transition.

Hence, the correct answer is option C.

Notes: In the Zeeman Effect, the orbitals shift up and down in energy depending on the magnitude and the sigh of the magnetic quantum number. In stark effect the shift depends only on the magnitude of the magnetic quantum number. The resulting spectral lines depend on the relative size of the field induced splittings compared to the separation between the multiplets.