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
A 41 year old married female presented with headache for the last 6 months. She had several consultations. All her investigations were found to be within normal limits. She still insists that there is something wrong in her head and seeks another consultation. The most likely diagnosis is: 
Select and explain. 
A. Phobia, B. Psychogenic headache, C. Hypochondriasis, D. Depression
C: Hypochondriasis
Answer: C: Hypochondriasis 
Explanation: The patient had multiple normal investigations but continues to believe that there is something wrong in her head and continues to seek multiple consultations. The most likely diagnosis is hypochondriasis. In DSM 5 : it is named as illness anxiety disorder