Which of the following orders must be adjusted accordingly on the ex-dividend date?

The correct answer focuses on the distinction between how different types of orders are treated in relation to the ex-dividend date. When a stock goes ex-dividend, it means that anyone purchasing the stock on or after this date will not receive the upcoming dividend payment.

In this context, a buy order with an "All or None" (AON) designation is designed to ensure that the order is executed in its entirety or not at all. On the ex-dividend date, the stock price is typically adjusted downwards to reflect the dividend payout. If the AON order is not adjusted to account for this price drop, it may not execute as intended. Thus, the price at which the order is set (15.75) must be adjusted downwards to reflect the decrease in value caused by the ex-dividend adjustment.

The other order types listed—such as the sell order and the "Do Not Reduce" order—do not require the same adjustment on the ex-dividend date. A sell order remains valid at the specified price without necessitating changes due to dividends. Similarly, a "Do Not Reduce" designation indicates that the order price should remain fixed, regardless of the dividend adjustment.

Thus, recognizing that buy orders that require specific conditions