Question

what is atomic mass?
o the mass of the atom based on the mass of an atom of oxygen - 16
o the mass of the atom based on the mass of an atom of hydrogen - 1
o the mass of an atom based on the mass of an atom of carbon - 12
o the mass of an atom based on the number of electrons

Explanation:

Atomic mass is defined relative to the mass of a carbon - 12 atom, which is assigned a mass of exactly 12 atomic mass units. Other atoms' masses are compared to this standard.

Answer:

the mass of an atom based on the mass of an atom of carbon-12