(d) The requirement is to identify the security that is
not suitable as a marketable investment. Answer (d) is correct
because convertible bonds are long-term investments that have
more risk than securities that are typically used for short-term
investment. The primary considerations regarding short-term
investments are liquidity and safety. Answers (a), (b), and (c)
are all appropriate as marketable investments. They are liquid
and have a low degree of risk.