The membership of such association shall consist solely of the following or any combination thereof:
(a) Members of police departments of municipal or public corporations or districts.
(b) Members of fire departments of municipal or public corporations or districts.
(c) Peace or law enforcement officers who are regular and salaried officers or employees of the state or of a single county or other political subdivision or public or municipal corporation.
(d) Persons who are emergency medical services personnel and employed by a fire department of a city, county, or district.
(e) Persons who at the time of becoming members of such association were qualified pursuant to subdivisions (a), (b), (c), or (d) of this section.