Electrons with energy 80 keV are incident on the tungsten target of an X-ray tube. K-shell electrons of tungsten have 72.5 keV energy. X- rays emitted by the tube contain only

• A. a continuous X-ray spectrum (Bremsstrahlung) with a minimum wavelength of \[\text{0}\text{.155}\overset{\text{o}}{\mathop{\text{A}}}\,\]
• B. a continuous X-ray spectrum (Bremsstrahlung) with all wavelengths
• C. the characteristic X-ray spectrum of tungsten
• D. a continuous X-ray spectrum (Bremsstrahlung) with a minimum wavelength of \[\text{0}\text{.155}\overset{\text{o}}{\mathop{\text{A}}}\,\]and the characteristic X-ray spectrum of tungsten..