If a referendum is not required, the district shall ensure that, at the time of the closing, the bonds met at least one of the following criteria:
(1) The bonds were rated in one of the highest four ratings by a nationally recognized rating service;
(2) The bonds were privately placed with or otherwise sold to accredited investors;
(3) The bonds were backed by a letter of credit from a bank, savings and loan association, or other creditworthy guarantor, or by bond insurance, guaranteeing payment of principal and interest on the bonds; or
(4) The bonds were accompanied by an independent financial advisory opinion stating that estimates of debt service coverage and probability of debt repayment are reasonable, which opinion was provided by an independent financial advisory, consulting, or accounting firm registered where professional registration is required by law and which is in good standing with the state and in conformance with all applicable professional standards for such opinions.