51. An auditor's consideration of a company's computer control activities has disclosed the following four circumstances. Indicate which circumstance constitutes a significant deficiency in internal control. a. Computer operators do not have access to the complete software support documentation. b. Computer operators are closely supervised by programmers. c. Programmers are not authorized to operate computers. d. Only one generation of backup files is stored in an off-premises location. (AICPA ADAPTED)