Which of the following is not an argument in favor of reforming the tax laws to encourage saving?

a. Saving is a key determinant of long-run prosperity.
b. Current tax laws discourage saving for the purpose of leaving a large bequest.
c. The substitution effect of a higher return to saving may be about equal to the income effect of a higher return to saving.
d. The tax code currently taxes some forms of capital income twice.

c