Chlorine, Which Exists in Nature in Two Isotopic Forms, Has

Chlorine, which exists in nature in two isotopic forms, has an atomic mass of 35.5 amu. This means that ________.

A) all chlorine atoms have masses of 35.5 amu
B) 35.5 amu is the upper limit for the mass of a chlorine atom
C) ³⁵Cl and ³⁷Cl each constitute approximately 50% of all chlorine atoms
D) ³⁵Cl constitutes 75% of full chlorine atoms, ³⁷Cl represents 25%