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 continuous X-ray spectrum (Bremsstrahlung) with a minimum wavelength of $\approx 0.155\stackrel{\text{0}}{\text{A}}$

A continuous X-ray spectrum (Bremsstrahlung) with all wavelengths

The characteristic X-ray spectrum of tungsten

A continuous X-ray spectrum (Bremsstrahlung) with a minimum wavelength of $\approx 0.155\stackrel{\text{0}}{\text{A}}$ and the characteristic X-ray spectrum of tungsten.