如图，已知∠AOB=120°，∠COD在∠AOB内部且∠COD = 60° ，则∠AOD与∠COB一定满足的关系为（ ）

A、∠AOD =∠COB

B、∠AOD + ∠COB = 180°

C、∠AOD = ∠COB

D、∠AOD + ∠COB = 120°