In the 1992 Studies Conducted by Baxter Et Al

In the 1992 studies conducted by Baxter et al., OCD patients were provided with cognitive-behavioral therapy (exposure and response prevention) but no drugs. This study is important because brain imaging showed that

A) the neurotransmitter circuits of the brain had been normalized.
B) the patients' OCD symptoms improved without changes in neurotransmitter function.
C) neither OCD symptoms nor neurotransmitter function had improved.
D) neurotransmitter circuits are the direct and only cause of OCD.