[单选题]
If an atom's atomic number is given by Z, its atma8 b p5ttze.u9y9a4*qkxo 9komic mass bz zb h((z6+nxhy A, and its neutron number by N, whn hz bz(6(zx+hich of the following is correct?
A. N = A + Z
B. N = Z - A
C. N = A - Z
D. none of the given answers
