Perhaps one recalls the ``hot phrase" stopping potential. The used in the photoelectric equation is essentially the stopping potential (energy). This memory-recall immediately narrows the choices down to just (A) and (C). Now, to find out if the potential is positive or negative.

FYI: The Photoelectric effect equation is basically just conservation of energy. One has , where is the kinetic energy of the electron as it accelerates through the medium between the cathode and collector, is the energy to free the electron from the metal, and is the energy given by the light source. Essentially, the energy from the photon first frees the electron from a sort of (valence) electron sea it lives in while in the metal, and then the excess energy propels it from cathode to collector in order to keep the current running. The minimum kinetic energy required to get the current going is the stopping potential (energy) . (According to the fight analogy below, the photon is the one who starts the fight, socking the electron off and away across the currents...)

The electron charge is negative and the potential must be a negative quantity in order to make positive overall.

(On the lighter side... The Photoelectric effect is also related to the Compton Effect. The effects can be seen as an arena fight. Think WWWF, but with electrons and photons. In PEE, the photon knocks the electron out, while in CE, the electron retaliates! It knocks the photon off course.)