The work functions of Caesium (Cs), potassium (K) and Sodium (Na) are   2.14 eV,2.30 eV and  2.75 eV respectively. If incident electromagnetic radiation has an incident energy of  2.20 eV, which of these photosensitive surfaces may emit photoelectrons?

Both Na and K K Only Na Only Cs Only

Cs Only

Here it is clear that energy of photon is more than the work function of Cs [Caesium] only.