What Is the Largest Tax Expenditure in the United States

What is the largest tax expenditure in the United States?

A) deduction of mortgage interest on owner-occupied houses
B) deferral of income from controlled foreign corporations -Consider This: While this is a tax expenditure,the amount involved does not compare to other areas where taxpayers benefit.
C) exclusion of employer contributions to health care and insurance
D) exclusion for interest earned on state and local government bonds