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: Physiology
Common precursor of mineralocoicoid, glucocoicoids and sex steroids ? 
Select and explain. 
A. Pregnenolone, B. a-hydroxyprogesterone, C. Dehydrotestosterone, D. Deoxycoisol
A: Pregnenolone
Answer: A: Pregnenolone 
Explanation: Ans. is 'a' i.e., Pregnenolone