Except as provided in subsection (b) of this section, this Part II of this subtitle applies to an individual who is: a member of the Employees’ Pension System or the Teachers’ Pension System; or a member of the Employees’ Retirement System or the Teachers’ Retirement System subject to Selection C (Combination Formula) as provided in § 22-221 of this article. This Part II of this subtitle does not apply to an individual who is: an employee of: a participating governmental unit that has not elected the contributory pension benefit for its employees under § 31-116 of this article; or a former participating governmental unit, other than Frederick County, that has withdrawn; a member of the Employees’ Pension System or Teachers’ Pension System who transferred from the Employees’ Retirement System or Teachers’ Retirement System after April 1, 1998; or a member who is subject to the Alternate Contributory Pension Selection under Part III of this subtitle.