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
All of the following are secreted proenzyme form except : 
Select and explain. 
A. Trypsin, B. Chymotrypsin, C. Pepsin, D. Ribonuclease
D: Ribonuclease
Answer: D: Ribonuclease 
Explanation: D i.e. Ribonuclease