creditable service
(1) Subject to any election under section 4046(b)(1)(C) of this title and unless otherwise expressly provided by any spousal agreement or court order under section 4060(b)(1) of this title , if a former participant who is entitled to receive an annuity is survived by a former spouse, the former spouse shall be entitled to a survivor annuity— (A) if married to the participant throughout the creditable service of the participant, equal to 55 percent of the full amount of the participant’s annuity, as computed under section 4046(a) of this title ; or (B) if not married to the participant throughout such creditable service, equal to that former spouse’s pro rata share of 55 percent of the full amount of such annuity. For the purposes of this paragraph, the term “creditable service” means service which is creditable under part I or II.