The Brainliest Answer!
The effect of rotation of earth changes the gravity
F = mg - mw²RSinФ
according value of force given we can write
mg/2 = mg -mw²RSinФ
g/2 = g - w²R (eliminating m and since at equater Ф =π/2 .SinФ =1)
Now solving we get 
w=√g/2R = angular velocity
therefore option c is answer

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