What type of account allows for the purchase of securities on margin?

A margin account is specifically designed to allow investors to borrow funds from a brokerage to purchase securities, thereby enabling them to buy more than they could with just their own capital. This borrowing is secured by the securities held in the account and typically involves the investor paying interest on the borrowed funds.

In contrast, a cash account requires that all transactions be paid for in full at the time of purchase, making it unsuitable for margin trading. Retirement accounts often have restrictions on margin trading as well, as they are designed to encourage long-term savings and investment for retirement. While a brokerage account is a general term that can encompass both cash and margin accounts, it does not specifically imply the ability to trade on margin. Therefore, the margin account is the correct answer for purchasing securities on margin due to its unique features that facilitate such transactions.