Choice "A" is correct. The IIA defines internal auditing as an independent objective assurance and consulting activity designed to add value and improve an organization's operations.
Choice "c" is incorrect. The IIA defines internal auditing as an independent rather than interdependent activity. The definition does not characterize internal auditing as an attest function.
Choice "b" is incorrect. Program audits or evaluations may be part of an internal auditor's work; however, the definition provided by the IIA characterizes internal auditing as an independent objective assurance and consulting activity.
Choice "d" is incorrect. Although the adding value and, by extension, institutional improvement, is a purpose of internal auditing, the IIA definition characterizes internal auditing as an independent objective assurance and consulting activity.