[单选题]
The nuclear energy levels of a nucleus are shown below. K, L, and M are transitions between energy levels.
Which statements are correct about photons emitted during transitions K, L, and M?
I. The wavelength of the photon emitted by transition K is greater than the wavelength of the photon emitted by transition L.
II. The frequency of the photon emitted by transition K is equal to the frequency of the photon emitted by transition M.
III. The wavelength of the photon emitted by transition L is greater than the wavelength of the photon emitted by transition M.
A. $I$ only
B. $I$ and $II$ only
C. $II$ and $III$ only
D. $I$, $II$ and $III$
