Corporate Bonds Are Less Marketable Than Money Market Instruments and Corporate

Corporate bonds are less marketable than money market instruments and corporate equities because

A) they have special features (e.g., call provisions) that make them difficult to value.
B) they are long-term securities, which tend to be riskier and less marketable.
C) both a and b
D) Corporate bonds are in fact not less marketable than money market instruments and corporate equities.