Choice "B" is correct. Significant audit findings do not include staffing changes at the client.
Choice "a" is incorrect. Discovery of a material sale recorded in the current year that properly belonged in the subsequent year represents a possible material misstatement in the financial statements. Possible material misstatements are considered to be significant audit findings.
Choice "c" is incorrect. When substantial doubt about an entity's ability to continue as a going concern exists, there is likely to be a modification to the auditor's standard report. Items resulting in report modifications are generally considered to be significant audit findings.
Choice "d" is incorrect. Matters related to the application of accounting principles to complex and unusual transactions are considered to be significant audit findings.