The Internal Revenue Code excludes from Federal gross income the interest on state and local government bonds. Which of the following correctly states the reason for this federal tax law?

a. If U.S. Congress included interest on state and local government bonds for Federal income tax purposes, this would be a violation of the states rights under the Tenth Amendment of the U.S. Constitution.

b. U.S. Congress is not legally prohibited from including interest on state and local government bonds for Federal income tax purposes. It simply has chosen not to do so up until now.

c. The United States Supreme Court has ruled that U.S. Congress can include interest on state and local government bonds for Federal income tax purposes if the statute complies with safeguards provided by the Tenth Amendment of the U.S. Constitution.

d. The United States Supreme Court has ruled that U.S. Congress can include interest on state and local government bonds for Federal income tax purposes if the statute complies with safeguards provided by the Seventh Amendment of the U.S. Constitution.

e. The legal reason is one that is not stated in any of the other choices.