Based on the Approximate Wavelength of Light Emitted by the Following

Based on the approximate wavelength of light emitted by the following materials, which one has the smallest band gap?

A) aluminum nitride, $\lambda$ = 206 nm
B) gallium nitride, $\lambda$ = 371 nm
C) indium nitride, $\lambda$ = 620 nm
D) boron-doped diamond, $\lambda$ = 675 nm
E) nitrogen-doped diamond, $\lambda$ = 425 nm