Which agency must approve the ethics rules promulgated by the PCAOB?

The correct answer is that the SEC (Securities and Exchange Commission) must approve the ethics rules promulgated by the PCAOB (Public Company Accounting Oversight Board). The PCAOB was established by the Sarbanes-Oxley Act of 2002 to oversee the audits of public companies in order to protect investors and ensure the integrity of the financial reporting process. While the PCAOB has the authority to set its own standards and rules, these standards are subject to review and approval by the SEC. This relationship underscores the importance of oversight within the financial regulatory framework, ensuring that the PCAOB's rules align with broader securities regulations and serve the public interest effectively.

The other options are not applicable in this context. The GAO (Government Accountability Office) primarily focuses on the accountability of federal government spending and performance, and it does not have the authority to approve PCAOB rules. The IRS (Internal Revenue Service) is focused on tax administration and compliance, which falls outside the scope of the PCAOB's responsibilities regarding auditing standards. Lastly, stating that no approval is necessary ignores the established regulatory framework in which the SEC plays a crucial role in approving the PCAOB’s rules.