Potassium Is Found in Nature Most Often as a Chloride

Potassium is found in nature most often as a chloride salt, whereas copper and mercury more often occur as the sulphides. The best explanation for this observation is

A) potassium is softer than copper or mercury.
B) the coinage metals are smaller than potassium.
C) the coinage metals prefer the +2 oxidation state.
D) potassium is less electronegative than copper.
E) the coinage metal ions are softer than potassium.