JEE Main Physics question

If the radius of the earth were suddenly to change to times its present value, with mass remaining unchanged, the new period of rotation of the earth would be given by

• (A)dT/dt=(T/r)(dr/dt)
• (B)dT/dt=(2T/r)(dr/dt)Correct
• (C)dT/dt=(r/T)(dr/dt)
• (D)dT/dt=(\frac12T/r)(dr/dt)