Choice "A" is correct. In auditing an entity's computerized payroll transactions, an auditor would be least likely to use test data to test controls concerning control and distribution of unclaimed checks, since these sorts of controls are typically not automated. Controls surrounding unclaimed checks typically rely on proper segregation of duties, which is best evaluated through the auditor's direct observation.
Choice "d" is incorrect. In auditing an entity's computerized payroll transactions, an auditor might use test data to test controls concerning overpayment of employees for hours not worked. For example, the auditor might input fictitious additional hours to determine whether any controls identify the problem.
Choice "b" is incorrect. In auditing an entity's computerized payroll transactions, an auditor might use test data to test controls concerning withholding of taxes and Social Security contributions. For example, the auditor might input fictitious amounts, or attempt to change the current amounts, to determine whether any controls identify the problem.
Choice "c" is incorrect. In auditing an entity's computerized payroll transactions, an auditor might use test data to test controls concerning missing employee identification numbers. For example, the auditor might try to input employee payroll data without an appropriate identification number, to determine whether any controls identify the problem.