The Atomic Mass of Naturally Occurring Fluorine, Which Exists in Nature

The atomic mass of naturally occurring fluorine, which exists in nature as a single isotope, is listed as 18.9984 u. This means that

A) all fluorine atoms found in nature have a mass that is 18.9984/12.000 times as great as that of a ¹²C atom.
B) all fluorine atoms found in nature have a mass that is 18.9984/1.0079 times as great as that of a ¹H atom.
C) some fluorine atoms found in nature have a mass that is 18.9984/12.000 times as great as that of a ¹²C atom.
D) some fluorine atoms found in nature have a mass that is 18.9984/1.0079 times as great as that of a ¹H atom.
E) no fluorine atom found in nature has a mass that is 18.9984/12.000 times as great as that of a ¹²C atom.