This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Miscellaneous (Obs), Subject name: Gynaecology & Obstetrics
[{'content': 'Commonest cause of primary amenorrhea: \nSelect and explain. \nA. Gonadal dysgenesis, B. Mullerian agenesis, C. Androgen insensitivity syndrome, D. Stein Levinthal syndrome', 'role': 'user'}, {'content': "Answer: A \nExplanation: Ans. A. Gonadal dysgenesis.Gonadal dysgenesis does not equate with turner's syndrome. There are many causes of gonadal dysgenesis in the female, most of which relate to abnormalities involving X chromosome e.g. Turner syndrome, turner mosaic, 46XY gonadal dysgenesis. 25% of girls with gonadal dysgenesis have 46XX karyotype. Turner syndrome is the most common form of gonadal dysgenesis", 'role': 'assistant'}]