About 5 months ago, you, the auditor, completed the audit of NS Ltd (NS) - a venture capital company that has since the audit gone into liquidation, after the auditors issued an Unqualified/Unmodified Audit Report. Apparently, the Directors colluded to fraudulently inflate sales and profits and intentionally mislead the auditors. NS expanded its operations over the last 10 years by buying smaller payment processing businesses and groups of customers around the world, including a 2020 move to take on 20,000 merchant clients of Citibank, spread over 11 Asia-Pacific countries-now subsidiaries of NS. It was this strategy that allowed NS to move profits and sales between their 100+ subsidiaries. The lead audit partner now realises that half of NS's revenue for the last 2 years and $6 billion in cash across its 12 subsidiaries did not exist. Which of the following statements MOST appropriately describes an audit procedure that would have uncovered NS's fraudulent activity?

a. The auditors should have scrutinized internal documents and conducted more interviews with staff to determine whether there was motivation and opportunity to commit fraud.

b. According to ASA240, the auditors are not responsible to uncover a concerted deception involving forged account documents.

c. The auditors should have confirmed all NS' cash bank balances directly with all the banks and that includes all subsidiaries' bank balances.

d. The auditor could have sourced a copy of the draft forensic audit report commissioned by 2 NS' Directors which investigated complaints from terminated staff that claimed there were fake journal entries performed by a number of staff on a regular basis