The Atomic Number for an Atom of a Specific Element

The atomic number for an atom of a specific element is equal to (Check all that apply)

A) the number of electrons in a single atom of that element.
B) the number of electrons plus neutrons in a single atom of that element.
C) the number of protons in a single atom of that element.
D) the number of neutrons and protons in a single atom of that element.
E) the position of an ion on the periodic table.