Until 2002 public accounting firms were self-regulated. Beginning in 2002, public accounting firms auditing SEC registrants became subject to the oversight of which entities?

The correct answer to this open question is the following.

Although there are no options attached, we can say the following.

Until 2002 public accounting firms were self-regulated. Beginning in 2002, public accounting firms auditing SEC registrants became subject to the oversight of the following entity: the Public Company Accounting Oversight Board, also known as PCAOB.

This organization was formed on July 30, 2002, after US Congress passed the Sarbanes-Oxley Act, which became an investor protection Act, generating accountability and transparency when auditing companies after the corruption issues that happened at that time.  

US Security and Exchange Commission oversees and has to approve any actions and changes of PCAOB when auditing companies or broker-dealers to present accurate, clear, and transparent reports.