A diffraction grating has 5000 lines per cm, what is its grating element?

Question

$\begin{array}{1 1} 2 \times 10^{-4}\;cm \\ 2 \times 10^{-3}\;cm \\ 2 \times 10^{4} \;cm \\ 2 \times 10^{3}\;cm \end{array}$