Step 1: Eugen Bleuler renamed dementia praecox as schizophrenia and viewed it as a group of disorders. He defined the fundamental (core) symptoms, popularly remembered as the 4 A's of Bleuler.
Step 2: The 4 A's are Ambivalence, Autism, Affect disturbances, and Association disturbances (which includes loosening of association). So options a, b, and c are all genuine Bleulerian fundamental symptoms.
Step 3: Hallucinations, along with delusions and negativism, were classified by Bleuler as accessory (secondary) symptoms, not fundamental ones. Since the question asks for the exception, hallucinations is the answer.