This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Gynaecology & Obstetrics
A 20-year-old young girl, presents with history of rapidly developing hirsutism and amenorrhea with change in voice. To establish a diagnosis you would like to proceed with which of the following tests in blood: 
Select and explain. 
A. 17 OH progesterone, B. DHEA, C. Testosterone, D. LH + FSH estimation
C: Testosterone
Answer: C: Testosterone 
Explanation: None