The money market is characterized by the trading of short-term financial assets, typically with maturities of one year or less. Among the options you've provided, the asset that would be traded on the money market is:
A bond sold at a face value of $100 offering a 0.5% annual yield and a 6-month maturity.
This bond has a short maturity period (6 months), which qualifies it for the money market. The other options have longer maturities or pertain to stocks, which are typically traded in capital markets rather than the money market.