A nurse is caring for a client who has posttraumatic stress disorder (PTSD) after being physically assaulted. The client is unable to recall any details of the event. Which of the following defense mechanisms should the nurse recognize that the client is displaying?

The correct answer is A: Dissociation. This defense mechanism involves detaching oneself from reality to cope with overwhelming stress. In this case, the client's inability to recall details of the traumatic event suggests dissociation as a way to protect themselves from the emotional pain associated with the assault.

Incorrect choices:
B: Rationalization - Involves justifying or making excuses for behaviors to reduce anxiety. This is not relevant to the client's memory loss.
C: Undoing - Involves attempting to reverse or negate a previous action. This is not applicable to the client's situation.
D: Reaction formation - Involves expressing the opposite of one's true feelings. This is not evident in the client's inability to recall the event.