Choice "D" is correct. Working papers should include the procedures that are applied and the conclusions reached in an audit engagement.Choice "a" is incorrect. The management representation letter is where the client asserts that all material matters have been adequately disclosed to the auditor.Choice "c" is incorrect. The accounting firm may have an overall audit guide on how to perform an audit, but it would not have the conclusions related to a specific audit. Choice "b" is incorrect. An auditor's report does not list the specific procedures used in an audit engagement.