As a result of studying MAYO FOUNDATION FOR MEDICAL EDUCATION AND RESEARCH, et al., Petitioners v. UNITED STATES, we can conclude:

a. that the MAYO case helps to distinguish existing distinctions between interpretive revenue rulings and legislative revenue rulings.

b. that the MAYO case introduced a different analysis than previously used in distinguishing between interpretive regulations and legislative regulations.

c. None of the other choices are correct.

d. that the MAYO case confuses existing distinctions between interpretive revenue rulings and legislative revenue rulings.

e. that the MAYO case reinforces the use of existing distinctions between interpretive regulations and legislative regulations.