Choice "B" is correct. Significant unexplained variances between standard and actual labor costs may cause the auditor to suspect an employee payroll fraud scheme.
Choice "d" is incorrect. Payroll checks generally are disbursed by the same person (or the same department) each payday, and this would not cause the auditor to suspect an employee payroll fraud scheme.
Choice "a" is incorrect. Time card approval by departmental supervisors is a standard practice, and would not raise an auditor's suspicions of a payroll fraud scheme.
Choice "c" is incorrect. Maintenance of a separate payroll bank account is a standard practice, and would not raise an auditor's suspicions of a payroll fraud scheme.