Which type of accounts are regulated under Regulation T?

Regulation T specifically governs margin accounts, which allow investors to borrow funds from broker-dealers to purchase securities. This regulation establishes the standards for the amount of credit that can be extended by brokers to investors for the purchase of securities and limits how much investors can borrow against the value of their securities. It sets forth initial margin requirements and maintenance requirements, which are crucial for managing risk in trading activities.

Cash accounts, on the other hand, do not involve borrowed funds; all transactions must be settled with the cash on hand in the account. As a result, these accounts are not subject to the same regulatory framework as margin accounts under Regulation T. This distinction is critical in understanding how different types of investment accounts operate within the regulatory landscape. Therefore, the correct choice focuses solely on margin accounts as being the ones regulated under Regulation T.