If the Tax Rate on Income Is Given by T

If the tax rate on income is given by t and the wage is given by w,what is the slope of the indifference curve at the optimal choice? (Assume that the person is not at a corner of the budget constraint.)

A) the slope of the indifference curve depends on preferences.
B) w - t + 1
C) w(t - 1)
D) w(1 - t)