Which of the following statements is correct without limitation? Select one: A Saving plans, life insurance contracts, and building loan contracts are practical examples of perpetuities. B. Annuity-immediate payments are always made at the end of the annuity period, whereas annuity-due payments are always made at the beginning of the corresponding period. C. The general calculation formula for the future value of an annuity is derived following the idea of an anthmetic series D. All statements are false