Cole, a financial advisor, has told his clients the following things. Which of his statements is not correct?

a$."$If you purchase a municipal bond, you can sell it before it matures."

b$."$U$.$S$.$ government bonds have the lowest default risk."

c$."$U$.$S$.$ government bonds generally pay a higher rate of interest than corporate bonds."

d$.$ "The interest recelved on corporate bonds is taxable."