If an unknown element has a mass number of 14 and you are told that it has 7 neutrons, how many protons does it have?
A. Substract the number of neutrons from the mass number = 7 protons
B. Substract the number of neutrons from the atomic number = 0 protons
C. Add the mass number to the number of neutrons = 21 protons
D. Add the mass number to the number of electrons = 21 protons