Explanation/Reference:
With CLIENT_ACKNOWLEDGEthe Session object relies on the application to call an acknowledge method on a received message. Once the method is called, the session acknowledges all messages received since the last acknowledge.
Incorrect Answers:
A: With CLIENT_ACKNOWLEDGEthe Session object acknowledges receipt of a message once the receiving application method has returned from processing it.
C: With DUPS_OK_ACKNOWLEDGEthe Session object acknowledges receipt of a message once the receiving application method has returned from processing it; duplicate acknowledges are permitted.
D: There is no acknowledge mode named DEFAULT_ACKNOWLEDGE.
Reference: http://docs.oracle.com/cd/E12840_01/wls/docs103/jms/fund.html