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
16-year-old girl presents with rapid onset hirsutism and amenorrhea. Best investigation is: 
Select and explain. 
A. Testosterone estimation, B. Dihydroepiandrosterone, C. Adrenocorticoids, D. LH and FSH estimation
A: Testosterone estimation
Answer: A: Testosterone estimation 
Explanation: None