The triangle formed by radii to the ends of a chord of a circle is an isosceles triangle. That means the central angle will be 180° less twice the base angle shown. .. ∠AOB = 180° -2*35° = 110° .. ∠COD = 180° -2*55° = 70°
Then the desired sum is .. ∠AOD +∠BOC = 360° -110° -70° = 180° . . . . . . corresponds to selection A