An investor is concerned with how changes in interest rates will affect the expected investment return of a Treasury bond if held to maturity. Which of the following types of risk is this?

Call risk pertains to the possibility that a bond may be redeemed by the issuer before its maturity date, typically during periods of declining interest rates. This risk does not directly relate to the reinvestment of cash flows from the bond itself, and it primarily affects callable bonds rather than non-callable Treasury bonds.

Event risk refers to unforeseen events that can significantly impact the value of a bond, such as natural disasters or corporate scandals. While these events can affect market conditions, they do not specifically relate to the impacts of changing interest rates on cash flow reinvestment for Treasury bonds.

Liquidity risk involves the difficulty of selling an asset without affecting its price significantly. While it is a concern for investors, it does not pertain to the effects of interest rate changes on the expected return of a bond held to maturity, which is more closely related to reinvestment strategy.