Which of the Following Statements About Tax Deferral Is True

Which of the following statements about tax deferral is true?

A) The value of tax deferral increases as the taxpayer's discount rate for computing NPV decreases.
B) Tax deferral is not an effective planning strategy if the taxpayer's marginal tax rate is stable over time.
C) The greater the length of time that the payment of a tax is deferred,the less the tax costs in NPV terms.
D) Both A and C are true.