A diatomic molecule having atoms of masses $m_{1}$ and $m_{2}$ has its potential energy function about the equilibrium position $r_{0}$ as given by $U(r)=-A+B\left(r-r_{0}\right)^{2}$, where $A$ and $B$ are constants. When the atom vibrate at high temperature condition, the square of angular frequency of vibration will be
(A) $\frac{2 B}{m_{1}}$
(B) $\frac{2 B}{m_{2}}$
(C) $\frac{2 B\left(m_{1}+m_{2}\right)}{m_{1} m_{2}}$
(D) $\frac{B\left(m_{1}+m_{2}\right)}{2 m_{1} m_{2}}$