Answer: B. less than 6%.
Step-by-step explanation:
Market interest rates have risen since the investor purchased the treasury bonds which means that the treasury bonds will be less sought after now because they offer a lower return than can be found in the market even if risk adjusted.
The investor will therefore only be able to sell it for a lower price which means that they will receive a lower rate for it. As we cannot say for certain what this rate will be, it is best to say that it will be under 6%.