Which primary PTSD symptom category was added to the diagnostic criteria for PTSD in the DSM-5 (2013) revisions that was not in the previous DSM versions (i.e., it resulted in 4 main symptom categories compared to the previous 3)?
a. Intrusion symptoms
b. Avoidance symptoms
c. Negative alterations in cognition and mood
d. Arousal and reactivity symptoms
