Which of the Following Is the Best Explanation of Why

Multiple Choice

Which of the following is the best explanation of why the mass of an atom is usually expressed in atomic mass units rather than grams?

A) An atomic mass unit is only used for carbon-12
B) The mass of one milliliter of water is one gram
C) The mass in grams is not known for atoms
D) The mass of an atom in grams is inconveniently small
E) Metric units such as grams are not applicable to atoms