What is the atomic mass?

I- It is the mass of an atom, which is the sum of the protons and electrons in the nucleus.
II- It is the mass of an atom, which is the sum of the protons and neutrons in the nucleus.
III- It is the mass of an atom, which is the sum of the electrons and neutrons in the nucleus.
a) Only I is correct.
b) Only II is correct.
c) Only III is correct.
d) I and II are correct.
e) II and III are correct.