The yield curve is upward sloping. A municipal bond has a higher interest rate than a Treasury bond. What could explain the municipal bonds higher interest rate in this case?

A The municipal bond has a shorter period to maturity than the Treasury bond

B The municipal bond trades more often than the Treasury bond (the muni is more liquid)

C The municipal bond has higher risk of default than the Treasury bond

D Treasury bonds do not pay federal tax, so they normally have a lower rate than municipal bonds