[单选题]
If an atom's atomic num- -rt kb-( vjpee)p2tvber is given by Z, its atomi5 x0rir hy5go3c mass by A, and its neutron numbe irr50hx3g oy5r by N, which of the following is correct?
A. N = A + Z
B. N = Z - A
C. N = A - Z
D. none of the given answers
