This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Neurotic, Stress Related and Somatoform Disorders, Subject name: Psychiatry
Which of the following statements differentiates Obsessional idea from delusion: 
Select and explain. 
A. Obsessional idea is not a conventional belief, B. Obsessional idea is held in spite of evidence to the contrary, C. Obsessional idea is regarded as senseless by patient, D. Obsessional idea is held on inadequate ground
C: Obsessional idea is regarded as senseless by patient
Answer: C: Obsessional idea is regarded as senseless by patient 
Explanation: Obsessions are considered senseless by the patient whereas patient has full belief in the delusions. For example, a patient who gets obsessive thoughts that "his hands are unclean" understands that his thought is not true and gets bothered by this repetitive thought whereas a patient with "delusion of infidelity" actually believes that his wife is cheating on him and continues to believes so irrespective of what others say.