Explanation

(d) Energy of a photon $E\ = \frac{hc}{\lambda}$
$\therefore$ Wavelength $\lambda = \frac{hc}{E}$
$= \frac{6.6\ \times \ 10^{- 34} \times \ 3\ \times {\ 10}^{8}}{13.2\ \times \ 10^{3}\ \times \ 1.6\ \times \ 10^{- 19}}$
$= \ 0.9375\ \times \ 10^{- 10}\ m$
$= \ 1\ \mathring{\mathrm{A}}$
Wavelength range of X-rays is from 10$^{-11}$ m to 10$^{-8}$ m $(0.1\ \mathring{\mathrm{A}}\ to\ 100\ \mathring{\mathrm{A}}).$
Therefore, the given electromagnetic radiation belongs to the X-ray region of electromagnetic spectrum.