Final answer:
Among the given options, the All or none (AON) order is the type that need not be immediately filled in its entirety. It can be carried out if and only if the entire quantity specified in the order can be filled.
Step-by-step explanation:
The order type among the mentioned options that need not be immediately filled in its entirety is the All or none (AON) order. An AON order specifies that the order can only be executed if the entire quantity can be filled, unlike Immediate or cancel (IOC) and Fill or Kill (FOK) orders that require immediate fulfillment. A Market at open order is to be executed at the first available price when the market opens, without any conditions on partial or immediate filling of the order.
Learn more about Order types