Which one is the wrong statement?

1. A
   The uncertainty principle is $\Delta E\times \Delta t\ge \frac{h}{4\pi }$
2. B
   Half-filled and fully filled orbitals have greater stability due to greater exchange energy, greater symmetry and more balanced arrangement
3. C
   The energy of $2s$ orbital is less than the energy of $2p$ orbital in case of Hydrogen like atoms
4. D
   de-Broglie's wavelength is given by $\lambda =\frac{h}{mv}$, where $m=$ mass of the particle, $v=$ group velocity of the particle