Answer:
Zero coupon Treasury bond with a duration equal to the investors investment horizon.
Step-by-step explanation:
Zero coupon Treasury bond is also called Treasury Zero and the face value of the bond is paid on maturity.
They do not pay interest periodically or coupon payment. Thus the name zero coupon.
This is in contrast to other bond types that make periodic payment of interest and then recieved face value at maturity.
Zero coupon Treasury bond minimises risk for the investor because the government always pays it's obligations.
The agreed value at maturity is not subject to market forces and other economic factors.
In this scenario when the zero coupon treasury bond has the same duration as investor investment horizon it minimises his risk compared to other bond types