Test of Controls

Please could you assist with the answer and an explanation to the following question:

“Which of the following procedures would provide the most reliable evidence that payroll calculations are checked by a payroll manager, is working effectively?
A Enquiry with the payroll clerk performing the payroll calculation
B Enquiry with the payroll manager performing the check
C Recalculation of the payroll amounts by the auditor
D Inspection of the payroll report for evidence that a sample of payroll amounts are checked.”

I selected option C in favour of D as, even though performing D confirms that a check has been performed, it does not tell you much about the quality of the check and, hence, whether the control is working effectively.

We might find that the payroll manager has signed the payroll report to evidence that he has checked the payroll calculations, but we might find that he was merely signing as a matter of routine and not actually checking if we recalculate the payroll amounts for a sample and subsequently find errors that were not identified by the manager.