C: Message Unit-of-Order is a WebLogic Server value-added feature that enables a stand-alone message producer, or a group of producers acting as one, to group messages into a single unit with respect to the processing order. This single unit is called a Unit-of-Order and requires that all messages from that unit be processed sequentially in the order they were created.
D Transactions required for parallel processing.
Incorrect:
A: Many applications need an even more restricted notion of a group than provided by the Message Unit-of-Order (UOO) feature. If this is the case for your applications, WebLogic JMS provides the Unit-of-Work (UOW) Message Groups, which allows applications to send JMS messages, identifying some of them as a group and allowing a JMS consumer to process them as such. For example, an JMS producer can designate a set of messages that need to be delivered to a single client without interruption, so that the messages can be processed as a unit. Further, the client will not be blocked waiting for the completion of one unit when there is another unit that is already complete.
Note:
* WebLogic JMS defines two default connection factories, which you can look up using the following JNDI names:
weblogic.jms.ConnectionFactory
weblogic.jms.XAConnectionFactory
Reference: Using Message Unit-of-Order