Which of the Following Statements Regarding the Black-Box Approach for Systems

Which of the following statements regarding the black-box approach for systems auditing is correct?

A) The auditors need to gain detailed knowledge of the systems' internal logic
B) The black-box approach could be adequate when automated systems applications are complicated
C) The auditors first calculating expected results from the transactions entered into the system. Then, the auditors compare these calculations to the processing or output results.
D) All of the above are correct