During a review of an application system, an IS auditor identifies automated controls designed to prevent the entry of duplicate transactions. What is the BEST way to verify that the controls work as designed? 

Answer options:

A. Implement periodic reconciliations.
B. Review quality assurance (QA) test results.
C. Use generalized audit software for seeking data corresponding to duplicate transactions.
D. Enter duplicate transactions in a copy of the live system.

A