(1) As used in this part 6, "acquiring corporation" means:
(a) Any stock insurance company organized under the laws of this state, other than the domestic company whose shareholders are to exchange their stock under a plan of exchange, as provided in this part 6; or
(b) Any stock corporation organized under the "Colorado Corporation Code" which is not an insurance company; or
(c) Any stock corporation which is not an insurance company and which was organized under any general law of this state prior to the effective date of the "Colorado Corporation Code" (January 1, 1959) and to which such code is applicable; or
(d) Any stock corporation organized under the laws of any state of the United States, whether or not an insurance company.