Serena has turned nonresponsive and has an expressionless face. she stays locked in her room for days and hardly ever moves or speaks. she does not complete any tasks, and exhibits catatonic behavior. given this scenario, which of the following statements is true of serena's condition? a) her behavior is a means of gaining medical attention. b) she shows symptoms of bipolar disorder. c) her condition can be diagnosed and treated easily. d) she exhibits negative symptoms of schizophrenia.