$13.$ Suppose an investor is considering one of two investments that are identical in all respects except for risk. If the investor anticipates a fair return for the risk of the security he invests in$,$ he can expect to $\_\_\_\_\_\_\_.$

a$.$ earn no more than the Treasury$-$bill rate on either security

b$.$ pay less for the security that has higher risk

c$.$ pay less for the security that has lower risk

d$.$ earn more if interest rates are lower