Ans : (b)
$E = \large\frac{1}{2} mv^2 = \large\frac{1}{2} m \bigg(\large\frac{h}{m\lambda} \bigg)^2\: \: \: \: \bigg[ \lambda= \large\frac{h}{mv} \bigg]$
$= \large\frac{1}{2} \large\frac{h^2}{2m \lambda^2}$
$E \: in \: eV = \large\frac{1}{2} \large\frac{h^2}{2mλ^2e}$
$= \large\frac{(6.63 \times 10^{-34} )^2}{ (2 \times 9.11 \times 10^{-31} \times 10^{-11} \times 10^{-11} \times 1.6 \times 10^{-19} )}$
$= 1.5 \times 10^4 \: eV= 15\: keV$