If g is acceleration due to gravity on the surface of the earth having radius R, the height above the surface of earth at which the acceleration due to g gravity reducer to\[\frac{g}{2}\]is

• A.  \[\frac{R}{2}\]                                 
• B.  \[(\sqrt{2}-1)R\]
• C.  \[R/\sqrt{2}\]                  
• D.  \[\frac{121R}{100}\]