Which of the following statements about variable annuities is true?

a. The periodic payments received by the annuitant are fixed.

b. Variable annuities typically provide a guaranteed death benefit payable to a beneficiary if the annuitant dies before the insurer has started making payments.

c. Insurers offering variable annuities are not permitted to charge administrative fees.

d. Although the value of annuity units fluctuates, accumulation units have a fixed value.