多项选择题What are the advantages of the realization of IIR filter in cascade form structure? A、Poles and zeros can be controlled separately. B、The zeros poles of all the second-order section can be interchanged, and the combination can be optimized to reduce the operation error. C、The errors of second-order networks do not affect each other, the total error is small and the requirement for wordlength is low. D、It can realize parallel operation and high-speed operation.