Electrons with energy `80 keV` are incident on the tungsten target of an X - rays tube , k- shell electrons of tungsten have `72.5 keV` energy X- rays emitted by the tube contain only
A. a continous X-ray spectrum (Bremsstrahlung) with a minimum wavelength of `~0.155 Å`
B. a continous X-ray spectrum (Bremsstrahlung) with all wavelengths
C. the characteristic X-ray spectrum of tungsten
D. a continous X-ray spectrum (Bremsstrahlung) with a minimum wavelength of `~0.155 Å` and the characteristic X-ray spectrum of tungsten