Backed by the U$.$S$.$ government, these financial instruments are short$-$term debt obligations with a maturity of less than one year. They are considered risk$-$free investments.

Issued by corporations, these unsecured debt instruments are used to fund corporate short$-$term financing requirements. If issued by a financially strong company, they have less risk.

These financial instruments are investment pools that buy such short$-$term debt instruments as Treasury bills $($T$-$bills$),$ certificates of deposit $($CDs$),$ and commercial paper. They can be easily liquidated.

Issued by corporations, these financial instruments give their holders a class ownership in a company. They are considered the most risky but provide higher expected returns.