Given that sphere $O$ has radius $1$, and a quadrangular pyramid has vertex at $O$ with the four vertices of its base all on the surface of sphere $O$. When the volume of this quadrangular pyramid is maximum, its height is\\
A. $\frac{1}{3}$\\
B. $\frac{1}{2}$\\
C. $\frac{\sqrt{3}}{3}$\\
D. $\frac{\sqrt{2}}{2}$