Which of the Following Is the Best Definition of the Atomic

Multiple Choice

Which of the following is the best definition of the atomic mass unit?

A) Exactly 1/12 of the mass of a carbon-12 atom
B) The average mass of the atoms of an element compared to an atom of carbon-12 at exactly 12 u
C) The total number of protons and neutrons in the nucleus of an atom of carbon-12
D) Exactly 1/12 of the mass of a carbon-12 nucleus
E) Exactly 1/12 of the mass of 12 neutrons in a neutral electrical field