A.the number of protons in the nucleus
B.the number of neutrons in the nucleus
C.the number of protons and neutrons in the nucleus
D.the difference in the number of protons and neutrons in the nucleus
A.the number of protons in the nucleus
B.the number of neutrons in the nucleus
C.the number of protons and neutrons in the nucleus
D.the difference in the number of protons and neutrons in the nucleus