[单选题]
If an atom's atomic numbe.(9vqs 1n r x4rbyeljko6:q e,g( tptbb4)z9mr 3gbqepcy/v zs )+o/bdz;7 6a qis given by Z, its atomic mass by A, and its neutron number by N, which of the following is correb7abzq;o c/dv+ )s3zgy6 peq/ct?
A. N = A + Z
B. N = Z - A
C. N = A - Z
D. none of the given answers