Which statement about an element's average atomic mass number is correct?
A) It is equal to one-twelfth the mass of the most common isotope.
B) It is based on an isotope's charge, so negatively charged isotopes have a great effect then positive ones.
C) It is determined by counting the number of isotopes in a sample of the element.
D) It is a weighted average, so common isotopes have a greater effect then uncommon ones.
D) It is a weighted average, so common isotopes have a greater effect than uncommon ones.
(this multiple choice question has been scrambled)