Insert the missing words:

Standards play a crucial role in internal auditing and support the concept of auditing as a professionally based discipline. It is however clear that published statements are of little use unless they have been fully implemented and subject to continual review. The

. . . . . . . . . . . . . . . . . is the right mechanism for this process and it is through this that formal standards may be set and adopted.

a. bonus scheme

b. audit manual

c. performance appraisal scheme

d. working paper file