The wavelength of a neutron with energy $1 \mathrm{eV}$ is closest to:

For a neutron of momentum  $p=\sqrt{2mE}$, where $E$ is the energy of the neutron, wavelength $\lambda$ of the neutron is

$\lambda =\frac{h}{p}=\frac{h}{\sqrt{2mE}}=\frac{6.63\times {10}^{-34}}{\sqrt{2\times 1.67\times {10}^{-27}\times 1.6\times {10}^{-19}}}=2.87\times {10}^{-11} \mathrm{m} \approx 0.3\times {10}^{-8} \mathrm{cm}$