Photoelectric effect is the phenomenon in which:

(A) Photons come out of a metal when it is hit by a beam of electrons
(B) Photons come out of the nucleus of an atom under the action of an electric field
(C) Electrons come out of a metal with a constant velocity which depends on the frequency and intensity of incident radiation
(D) Electrons come out of a metal with different velocities not greater than a certain value which depends only on the frequency of the incident light and not on its intensity