The mass of one atom would best be measured in this unit: a. amu b. gram c. milligram d. microgram

The mass of one atom is measured in amu units

Explanation:

 The number of protons determines what atom we are looking at (e.g., all atoms with six protons are carbon atoms); the number of protons in an atom is called the atomic number.    

The atomic mass of the atom is the mass of the protons plus the mass of the neutrons, 6 + 7

a unit of mass used to express atomic and molecular weights, equal to one twelfth of the mass of an atom of carbon-12.

Atomic mass is extremely important in chemistry because it is the connection between mass, which we can measure in the laboratory, and moles, which are numbers of atoms. Most of what we study in chemistry is determined by ratios of atoms.