单项选择题

A.n(A)·G(A)+n(B)·G(B)
B.n(A)·μ(A ,m)+n(B)·μ(B ,m)
C.n(A)·G⊖(A ,m)+n(B)·G⊖(B ,m)
D.n(A)·μ⊖(A ,m)+n(B)·μ⊖(B ,m)