(a) Prior to the effective date of retirement, but not thereafter, except as provided in subsection (c) of this section, a member may elect to receive retirement income payments in the normal form, or the actuarial equivalent of the normal form from the following options:
(1) Option A — Joint and Survivor Annuity. — A life annuity payable during the joint lifetime of the member and his or her beneficiary who is a natural person with an insurable interest in the member's life. Upon the death of either the member or his or her beneficiary, the benefit shall continue as a life annuity to the survivor in an amount equal to fifty percent, sixty-six and two-thirds percent, seventy-five percent or one hundred percent of the amount paid while both were living as selected by the member. If the retiring member is married, the spouse shall sign a waiver of benefit rights if the beneficiary is to be other than the spouse.