互补 
互补[-補] hùbǔ* {E} v. help each other; complement ◆attr. 〈lg.〉 complementary
互补 互补 [hùbǔ] complementary; to complement each other 
互 互 mutually / - / ceiling snout mutually 補 补 supplement / - / cloak dog tag supplement L5-6 互补 hùbŭ (VS)