What is the difference between atomic mass, atomic weight, and molar mass?

• A. atomic mass: the sum of the number of protons and neutrons in an element
  atomic weight: the weighted average of the masses of an element's naturally occurring isotopes
  molar mass: the mass (in g) of one mole of an element or compound
• B. atomic mass: the mass of a single atom of an element or isotope
  atomic weight: the weighted average of the masses of an element's naturally occurring isotopes
  molar mass: the mass (in g) of one mole of an element or compound
• C. atomic mass: the mass of a single atom of an element or isotope
  atomic weight: the sum of the number of protons and neutrons in an element
  molar mass: the number of protons in an element
• D. atomic mass: the number of protons in an element
  atomic weight: the mass of a single atom of an element or isotope
  molar mass: the weighted average of the masses of an element's naturally occurring isotopes

Answer: (B)