Answer:
Short-term debt obligations of the U.S
Step-by-step explanation:
The treasury bills are the marketable securities that are issued by the US government to fund its personal operations. The money is raised to finance the economy for a shorter term and later the country payback the principal along with its interest.
These securities the least associated risk and thats the reason they are also known as risk free investments because there is no risk that the investment will not earn any return.