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
Regarding obsessive compulsive disorder, which of the following is true? 
Select and explain. 
A. Most common obsession is obsession of contamination, B. Most common compulsion is compulsion of checking, C. Obsession is a disorder of possession of thought, D. All the above are true
D: All the above are true
Answer: D: All the above are true 
Explanation: All the three statements are correct. Please remember that, obsessions are disorders of 'possession' of thought. In some cases, possession is not in the option, in that scenario, the second best answer is, content of thought