In paschen series electron transmits from some higher state to n=3‌states
So photons of paschen series have energies ranging from : Emin=En=4−En=3 =−0.85−(−1.5l) =0.66‌eV to Emax=En=∞−En=3 =0−(−1.5l) =1.51‌eV So, if a photon of paschen series able to emit a photoelectron from a metal, then work function φ0 of metal must be such that, φ0≤ Photon energy or φ0≤1.51‌eV Only matching option is options (c) and (d).