Every metal has a definite work function. Why do all photo electrons not come out with the same energy if incident radiation is monochromatic ? why there an energy distribution of photo electron ?

Question

$\begin{array}{1 1} \text{For a given incident radiation electron off from difference levels come out with difference energies } \\ \text{All electrons do not occupy a continuous band of levels} \\ \text{work function indicates the minimum energy required for the electrons in the highest level of the conduction band to get out of the metal } \\ \text{None of the above } \end{array} $