The stopping potential of photo-electrons depends upon:

both the frequency of the incident light and the material of the cathode.

The correct answer is Option (3) → both the frequency of the incident light and the material of the cathode.

Stopping potential is determined by the maximum kinetic energy of photoelectrons:

$K_{\max} = e V_0 = h \nu - \phi$

where $\nu$ = frequency of incident light, $\phi$ = work function of cathode material.

Thus, $V_0$ depends on both the frequency of incident light and the material (work function), but not on the intensity.

Answer: both the frequency of the incident light and the material of the cathode.