A 34-year-old woman with posttraumatic stress disorder has been treated with exposure therapy, with partial success. Her clinician is considering an adjunct medication. The agent d- cycloserine could be efficacious for reducing symptoms in anxiety disorders because it has been shown to: A. Increase glutamate neurotransmission during fear conditioning B. Decrease glutamate neurotransmission during fear conditioning C. Increase glutamate neurotransmission during fear extinction D. Decrease glutamate neurotransmission during fear extinction