Which agency is responsible for protecting investors and maintaining fair and efficient markets?

The Securities and Exchange Commission (SEC) is the agency designated with the responsibility for protecting investors and ensuring the integrity of the securities markets. The SEC's primary functions include enforcing federal securities laws, regulating the securities industry, and overseeing the securities exchanges. By doing so, it aims to promote a fair and orderly market, which is crucial for maintaining investor confidence and protecting participants from fraudulent activities.

The SEC's regulatory framework involves requiring public companies to disclose essential financial information, thereby providing transparency and enabling investors to make informed decisions. This oversight helps maintain market efficiency and fairness by ensuring that all investors have access to the same critical information.

In contrast, the Financial Industry Regulatory Authority (FINRA) specifically focuses on regulating brokerage firms and exchange markets, while the Consumer Financial Protection Bureau (CFPB) is concerned with protecting consumer financial interests in general, rather than specifically focusing on investors in the securities market. The American Stock Exchange (AMEX) serves as an actual exchange where securities are traded, rather than an agency focused on regulatory oversight.

Thus, the SEC is fundamentally positioned as the main authority responsible for investor protection and maintaining market integrity, making it the correct choice.