Explanation

(d) Given : $E = 13.2keV$
$\lambda(in\ \mathring{\mathrm{A}}) = \frac{hc}{E(eV)} = \frac{12400}{13.2 \times 10^{3}} = 0.939\mathring{\mathrm{A}} = 1\mathring{\mathrm{A}}$
$X$-rays covers wavelengths ranging from about $10^{- 8}m(10nm)$ to $10^{- 3}m\left( 10^{- 4}nm \right).$
An electromagnetic radiation of energy $13.2\ keV$ belongs to $X$-ray region of electromagnetic spectrum