Firmly held, unshakable beliefs with no basis in reality, and they commonly occur with schizophrenia.

Delusion

Explanation:

Delusion is the form of schizophrenia. Delusions are reinforced by the misinterpretation of the situation. This delusion includes many types of [paranoia. Delusions are of many types such as  

There are different types of treatment been provided to the patient. Cognitive behavior therapy, family therapy, group therapy, etc. have been given to the patient. Many anti-psychotic drugs are there which is useful in the treatment of delusions.  

answer; i believe the correct answer is (a) the correlation between the cause variable and outcome variable is zero;