If earth is supposed to be a sphere of radius R , if `g_(30)` is value of acceleration due to gravity at latitude of `30^(@)` and g at the equator, the value of `g-g_(30^(@))` is
A. `1/4 omega^(2)R`
B. `3/4 omega^(2)R`
C. `omega^(2) R`
D. `1/2 omega^(2)R`