According to DSM-5, which of the following is true of the symptoms of schizophrenia?
a. The characteristic symptoms of the condition interfere with social or occupational function of an individual.
b. An individual experiences a manic episode, perhaps alternating with periods of depression.
c. The characteristic symptoms of the condition are observed for a duration of up to three months.
d. An individual exhibits grossly disorganized behavior and negative symptoms for at least two weeks.