Which of the following statements is correct?

a. changes in the federal funds rate usually will result in changes in both short-term and long-term interest rates on financial assets.
b. the effect of a change in the federal funds rate on long-term interest rates is usually smaller than it is on short-term interest rates.
c. a majority of economists support the fed's choice of the interest rate as its monetary policy target, but some economists believe the fed should concentrate on the money supply instead.
d. all of the above are true.