If m is mass of electron, v its velocity, r the radius of stationary circular orbit around a nucleus with charge Ze, then from Bohr's first postulate, the kinetic energy \[K=\frac{1}{2}m{{v}^{2}}\]of the electron in C.G.S. system is equal to [NCERT 1977]

• A.   \[\frac{1}{2}\frac{Z{{e}^{2}}}{r}\] 
• B.   \[\frac{1}{2}\frac{Z{{e}^{2}}}{{{r}^{2}}}\]
• C.   \[\frac{Z{{e}^{2}}}{r}\]     
• D.   \[\frac{Ze}{{{r}^{2}}}\]