[单选题]
If an atom's atomic nu:f7 : mqp 7lrm0;tuo tm dh96tme:okw1mbe*ppw g:(fi r0qr is given by Z, its atomic mass by A, and its neutron number by N, wigq0p f :p(wr*hich of the following is correct?
A. N = A + Z
B. N = Z - A
C. N = A - Z
D. none of the given answers
