Which of the Following State Taxes Is Unconstitutional

Multiple Choice

Which of the following state taxes is unconstitutional:

A) Hawaii imposed a 20 percent tax on all alcoholic beverages except for local products
B) Michigan exempted from state income taxes the retirement benefits paid to state employees, but taxed all other retirement income, such as retired federal government employees' benefits
C) North Dakota imposed state sales taxes on out-of-state firms doing mail-order business with North Dakota residents
D) all of the other specific choices are unconstitutional
E) none of the other specific choices are unconstitutional