Mark out the correct statement regarding X-rays.
A. When fast moving electrons strike the metal target, they enter the metal larged and in a very short time span come to rest , and thus an electromagnetic charged electron produces electromagnetic waves (X-ray).
B. Characteristic X-rays are produced due to transition of an electron from higher energy levels to vacant lower energy levels.
C. X-ray spectrum is a discrete spectra just like hydrogen spectra.
D. Both (a) and (b) are correct.