Final answer:
Reg. T doesn't apply to U.S. Treasury securities or options.
Step-by-step explanation:
The answer to the question is D) U.S. Treasury securities, options. Reg. T, also known as Regulation T, is a rule established by the Federal Reserve Board that governs the amount of credit that brokers and dealers can extend to their customers for the purchase of securities. However, Reg. T does not apply to U.S. Treasury securities or options on those securities.