38. Which of the following statements concerning the timing of IRA deductible contributions is (are) correct? a. To be deductible for this year, the contribution must be made by April 15th next year. b. An extension for filing a taxpayer's final tax form grants the taxpayer the same extension for making a deductible IRA contribution. c. Contributions must be made by December 31 of the year for which they are to be deducted. d. Contributions must be made by December 31 of the year for which they are to be deducted, but the decision of whether to deduct must be made by April 15 of the following year