Which of the following statements is correct regarding an auditor placing reliance on internal controls to assess control risk at less than maximum?

a) The auditor may place such reliance as long as they have determined the design of such controls to be adequate

b) The auditor of a non-issuer is not permitted to place reliance on internal controls as they are not performing an integrated audit

c) The auditor is required to perform tests of the operating effectiveness of significant internal controls before such reliance can be placed

d) The auditor may place such reliance as long as they have verified that the controls were implemented with a walkthrough