Sodium and Copper have work functions $2.3\: eV\: and \: 4.5\: eV$ respectively. Then the ratio of the wavelengths is nearest to

Question

$\begin {array} {1 1} (a)\;1:2 & \quad (b)\;4:1 \\ (c)\;2:1 & \quad (d)\;1:4 \end {array}$