Photoelectric emission occurs only if the incident energy $E$ is greater than or equal to the work function $\phi$ of the metal. Given $E = 2.20$ eV. For Cs, $\phi = 2.14$ eV. Since $2.20 > 2.14$, Cs will emit photoelectrons. For K, $\phi = 2.30$ eV and for Na, $\phi = 2.75$ eV. Since $2.20 < 2.30$ and $2.20 < 2.75$, neither K nor Na will emit photoelectrons.