@mystical guy thanks for the answer. I wrote to Becker and here is what they had to say:
Your answer was likely correct – but only through last June. When the Clarified Audit Standards became testable as of July 1, 2013, the AICPA determined that although both the ‘old' standards (AU) and the Clarified standards (AU-C) would be presented in the research tool, ONLY answers from the Clarified standards would be accepted as correct. So, unfortunately, even if your answer was right, the AICPA would count it wrong – basically what happened on this question.
Here's an extra wrinkle for your exam. The ‘old' standards were officially retired from being tested on the exam as of January 1, 2014. As a result, the AICPA should purge the old standards from the research tool leaving only the Clarified standards. Until we've received confirmation from the AICPA that it's been done, we're leaving our research tool as it appeared in 2013.
Bottom line – if you see both AU and AU-C when you are working on your exam, make sure to select a response from the AU-C. If you only see AU, then that's where you'll find the answer.