A glass beaker has diameter `4cm` wide at the bottom. An observer observes the edge of bottom when beaker is empty as shown in figure. When the beaker is completely filled with liquid of refractive index `n=sqrt(5//2)`, he can just see the centre of bottom, then the height of glass beaker is :
A. `4 cm`
B. `sqrt(5//2) cm`
C. `16 cm`
D. None of these