An audit client is using a computer program to process financial data. The auditor's goal is to verify that transactions are processed correctly. There is no appropriate audit program available. Which of the following approaches most appropriately achieves the auditor's goal? 

a. The controlled reprocessing approach where the auditor verifies that a program to be tested is the one used to process actual data. 

b. The test data approach where the auditor includes several examples of each type of transaction error 

c. The parallel simulation approach where the auditor runs client data through a generalized audit software program and the client's program. 

d. The integrated test facility approach where audit data is processed in the client's system along with the client's data.