A model for quantized motion of an electron in a uniform magnetic field $B$ states that the flux passing through the orbit of the electron is $n(h/e)$ where $n$ is an integer, $h$ is Planck's constant and $e$ is the magnitude of electron's charge. According to the model, the magnetic moment of an electron in its lowest energy state will be ($m$ is the mass of the electron):

1. A
   $\frac{he}{\pi m}$
2. B
   $\frac{he}{2\pi m}$
3. C
   $\frac{heB}{\pi m}$
4. D
   $\frac{heB}{2\pi m}$