Which of the following statements is true concerning deductions "for" and "from" adjusted gross income (A.G.I.)?

a. A deduction from A.G.I. has no effect on the taxpayer's self-employment tax liability.

b. Corporations, like individuals, must classify their deductions as deductions for and from A.G.I.

c. Misclassification of a deduction for A.G.I. has no effect on the taxpayer's tax liability, assuming the taxpayer itemizes her or his deductions.

d. Misclassification of a deduction for A.G.I. never has an effect on the taxpayer's medical expense deduction.