Eligibility service for a member consists of service credit:
(1) for employment as a member;
(2) regained under § 24-304 of this subtitle by a member who redeposits accumulated contributions previously withdrawn;
(3) transferred from a retirement or pension system under Title 37 of this article;
(4) for military service as provided in Title 38 of this article; or
(5) purchased under this subtitle.