The correct answer is: C. stop-loss order.
A stop-loss order is an order to sell a security once the price of the security reaches a specified price. This type of order can be used to protect against losses in a volatile market.
A market order is an order to buy or sell a security at the best available price. This type of order is executed immediately, but it may not be executed at the price you want.
A limit order is an order to buy or sell a security at a specified price or better. This type of order is not executed immediately, but it will be executed if the price of the security reaches your specified price.
A contingency order is an order to buy or sell a security based on the occurrence of a certain event. This type of order is not commonly used, but it can be useful in certain situations.
In the case of a very volatile stock, it is important to use an order that will protect you from losses. A stop-loss order is the best option for this purpose.