Answer:The measure of arc DEF is 204°B is correctStep-by-step explanation:In a circle center at O. ∠DOF and ∠DEF are lie on same base but ∠DOF at center and ∠DEF on circle. Thus, ∠DOF = 2 ∠DEF minor ∠DOF = 2 x 78 = 156°We need to find arc DEF. DEF is central angle of major∠DOF major∠DOF + minor ∠DOF = 360° (Complete angle at center) major∠DOF + 156° = 360° major∠DOF = 204° major∠DOF is arc DEF. Hence, The measure of arc DEF is 204°