An individual who has been experiencing persistent anxiety for the past 6 months and unable to specify the cause or source of her nervous feelings likely suffers from

A) schizophrenia.
B) post-traumatic stress disorder.
C) a panic disorder.
D) generalized anxiety disorder.

The individual's symptoms suggest generalized anxiety disorder, which is characterized by persistent and excessive worry or anxiety about a variety of different things and situations, even when there is no apparent cause or trigger. Schizophrenia is characterized by delusions, hallucinations, and disordered thinking, which are not indicated in the scenario provided. Post-traumatic stress disorder is typically associated with symptoms that arise after experiencing or witnessing a traumatic event, which is not mentioned in the scenario. Panic disorder is characterized by recurrent, unexpected panic attacks, which are not mentioned as the individual is only experiencing persistent anxiety.