[单选题]
In a nuclear reaction, what value9 )cd fur3gk.p5+k2 44w wovul /otz ;n*cvbtk is conserved in addition to electric charge, en o4u2 n wv4bt;*wozk v/l+tk5cergy, and momentum?
A. atomic number
B. neutron number
C. nucleon number
D. none of the given answers
