Which statement is correct concerning the relevance of various types of controls to a financial audit?

a. An auditor may ordinarily ignore a consideration of controls when a substantive audit approach is taken.

b. Controls over the reliability of financial reporting are ordinarily most directly relevant to an audit, but other controls may also be relevant.

c. Controls over safeguarding of assets and liabilities are of primary importance, while controls over the reliability of financial reporting may also be relevant.

d. All controls are ordinarily relevant to an audit.