Which of the Following Statements About Marginal Tax Rates Is

Which of the following statements about marginal tax rates is false?

A) A taxpayer's marginal rate does not change over time.
B) As the marginal rate decreases, the after-tax cost of a deductible expense increases.
C) As the marginal rate decreases, the after-tax value of an income-generating transaction increases.
D) Statements A.and B.are false.