参考答案：D

解析：According to the DSM-IV, schizoaffective disorder refers to clients suffering from schizophrenia with elements of a mood disorder, either mania or depression. The prognosis is generally better than for the other types of schizophrenia, but it's worse than the prognosis for a mood disorder alone. Option C is incorrect because personality disorders and psychotic illness aren't listed together on the same axis. Option A is incorrect because schizophrenia is a major thought disorder and the question asks for elements of another disorder. Option B is incorrect because clients with schizoaffective disorder aren't suffering from schizophrenia and an amnestic disorder.